Positive resist composition and pattern-forming method

ABSTRACT

A positive resist composition includes: (A) a resin capable of increasing the solubility in an alkali developing solution by the action of an acid, including: (a1) a repeating unit selected from repeating units represented by specific formulae (a1-1) to (a1-3); (a2) a repeating unit represented by a specific formula (a2); and (a3) a repeating unit selected from repeating units represented by specific formulae (a3-1) to (a3-4); (B) a compound capable of generating an acid upon irradiation with actinic ray or radiation, (C) a resin including: at least one of a fluorine atom and a silicon atom; and a group selected from specific groups (x) to (z):(x) an alkali-soluble group, (y) a group capable of decomposing by the action of an alkali developing solution to increase the solubility in the alkali developing solution, and (z) a group capable of decomposing by the action of an acid; and (D) a solvent.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a positive resist composition for usein the manufacturing processes of semiconductors such as IC and thelike, liquid crystals, the manufacture of circuit substrates for thermalheads and the like, and lithographic processes of otherphoto-fabrications, and also relates to a pattern-forming method usingthe same. In particular, the invention relates to a positive resistcomposition suitable for exposure with an immersion projection exposureapparatus using far ultraviolet rays of wavelengths of 300 nm or less asa light source, and a pattern-forming method using the same.

2. Description of the Related Art

With the progress of fining of semiconductor devices, shortening of thewavelengths of exposure light source and increasing of the numericalaperture of the projection lens (high NA) have advanced, and nowexposure apparatus of NA 0.84 using an ArF excimer laser havingwavelength of 193 nm as a light source have been developed. As generallyknown, this can be expressed by the following expressions:

(Resolution)=k ₁·(λ/NA)

(Depth of focus)=±k ₂ ·λ/NA ²

wherein λ is the wavelength of exposure light source, NA is thenumerical aperture of the projection lens, k₁ and k₂ are thecoefficients concerning the process.

For further higher resolution by the shortening of wavelengths, anexposure apparatus with an F₂ excimer laser having wavelength of 157 nmas the light source has been studied, however, the materials of lens foruse in the exposure apparatus and the materials of resist are extremelyrestricted for shortening of wavelengths, so that the realization of thereasonable manufacturing costs of the apparatus and materials andquality stabilization are very difficult, as a result, there arepossibilities of missing an exposure apparatus and a resist havingsufficient performances and stabilities within a required period oftime.

As a technique for increasing resolution in the optical microscope, whatis called an immersion method of filling between a projection lens and asample with a liquid of high refractive index (hereinafter also referredto as “an immersion liquid”) has been conventionally known.

As “the effect of immersion”, the above resolution and depth of focus inthe case of immersion can be expressed by the following expressions,taking λ₀ as the wavelength of the exposure light in the air, n as therefractive index of immersion liquid to the air, and NA₀=sin θ with θ asconvergence half angle of the ray of light:

(Resolution)=k ₁·(λ₀ /n)/NA)₀

(Depth of focus)=±k ₂·(λ₀ /n)/NA ₀ ²

That is, the effect of immersion is equivalent to the case of usingexposure wavelength of the wavelength of 1/n. In other words, in thecase of the projection optical system of the same NA, the depth of focuscan be made n magnifications by immersion. This is effective for everypattern form, and can be combined with super resolution techniques suchas a phase shift method and a deformation lighting method.

The apparatus applying this effect to the transfer of micro-fine imagepattern of semiconductor device are introduced by JP-A-57-153433, theterm “JP-A” as used herein refers to an “unexamined published Japanesepatent application” and JP-A-7-220990.

The latest technical advancement of immersion exposure is reported inSPIE Proc. 4688, 11 (2002), J. Vac. Sci. Tecnol. B, 17 (1999), SPIEProc., 3999, 2 (2000), and WO 2004/077158.

When an ArF excimer laser is used as the light source, it is thoughtthat pure water (refractive index at 193 nm: 1.44) is most promising inthe light of the safety in handling, and the transmittance and therefractive index at 193 nm. When an F₂ excimer laser is used as thelight source, a solution containing fluorine is examined from thebalance of the transmittance and the refractive index at 157 nm, butfrom the viewpoint of environmental safety and in the point ofrefractive index, a sufficiently satisfactory solution has not beenfound yet. From the extent of the effect of immersion and the degree ofcompletion of resist, it is thought that immersion exposure techniquewill be carried on the ArF exposure apparatus earliest.

From the advent of the resist for a KrF excimer laser (248 nm) on, animage-forming method that is called chemical amplification is used asthe image-forming method of the resist for compensating for thereduction of sensitivity by light absorption. To explain theimage-forming method of positive chemical amplification by example, thisis an image-forming method of exposing a resist to decompose an acidgenerator in the exposed part to thereby generate an acid, utilizing thegenerated acid as the reactive catalyst to change an alkali-insolublegroup to an alkali-soluble group by the bake after exposure (PEB: PostExposure Bake), and removing the exposed part by alkali development.

The resist for an ArF excimer laser (wavelength: 193 nm) using thechemical amplification mechanism is now being a main current, but thereis a drawback that a formed pattern falls down and results in the defectin manufacturing a device, and improvement is required.

When a chemical amplification resist is applied to immersion exposure,it is appointed that since the resist layer inevitably touches animmersion liquid at the time of exposure, the resist layer decomposesand ingredients that adversely influence the immersion liquid ooze fromthe resist layer. WO 2004/068242 discloses that the resist performancechanges by the immersion of a resist for ArF exposure in water beforeand after exposure and appoints this is a problem in immersion exposure.

Further, when immersion exposure is carried out, there are cases wherecircular defects called water marks occur on account of the dropletsremaining on a resist film after exposure, and improvement is required.

SUMMARY OF THE INVENTION

In consideration of the above, the invention provides a positive resistcomposition capable of restraining the occurrence of water marks at thetime of immersion exposure, and also provides a pattern-forming methodusing the same.

<1> A positive resist composition comprising:

(A) a resin capable of increasing the solubility in an alkali developingsolution by the action of an acid, comprising:

-   -   (a1) a repeating unit selected from repeating units represented        by following formulae (a1-1) to (a1-3);    -   (a2) a repeating unit represented by a following formula (a2);        and    -   (a3) a repeating unit selected from repeating units represented        by following formulae (a31) to (a34);

(B) a compound capable of generating an acid upon irradiation withactinic ray or radiation,

(C) a resin comprising:

-   -   at least one of a fluorine atom and a silicon atom; and    -   a group selected from following groups (x) to (z);        -   (x) an alkali-soluble group,        -   (y) a group capable of decomposing by the action of an            alkali developing solution to increase the solubility in the            alkali developing solution, and        -   (z) a group capable of decomposing by the action of an acid;            and

(D) a solvent:

wherein

R represents a hydrogen atom, a halogen atom, or an alkyl group;

R′ represents an acid-decomposable group;

each of R₁₂ and R₁₃ independently represents a hydrogen atom, a methylgroup, an ethyl group, or a propyl group;

R₁₄ represents an alicyclic group; and

n represents an integer of from 0 to 5.

<2> The positive resist composition as described in <1>, wherein

the resin (A) further comprises:

-   -   (a4) a repeating unit selected from repeating units represented        following formulae (a4-1) to (a4-3):

wherein

R represents a hydrogen atom, a halogen atom, or an alkyl group.

<3> The positive resist composition as described in <1> or <2>, wherein

the resin (C) comprises a repeating unit containing a lactone group.

<4> The positive resist composition as described in <1> or <2>, wherein

the resin (C) is an alkali-soluble resin containing an alkyl grouphaving a fluorine atom and from 1 to 4 carbon atoms, a cycloalkyl grouphaving a fluorine atom, or an aryl group having a fluorine atom,

<5> The positive resist composition as described in <1> or <2>, wherein

the resin (C) contains an alcoholic hydroxyl group, and

an alcohol moiety of the alcoholic hydroxyl group is a fluorinatedalcohol.

<6> The positive resist composition as described in any one of <1> to<5>, wherein

the solvent (D) is a mixed solvent of two or more kinds of solventscomprising propylene glycol monomethyl ether acetate.

<7> The positive resist composition as described in any one of <1> to<5>, wherein

the solvent (D) is a mixed solvent of two or more kinds of solventscomprising ethyl lactate and propylene glycol monomethyl ether acetate.

<8> The positive resist composition as described in any one of 1< > to<7>, further comprising;

(E) a basic compound.

<9> The positive resist composition as described in any one of <1> to<8>, wherein

the compound (B) has a triphenyl sulfonium cation structure.

<10> The positive resist composition as described in any one of <1> to<9>, wherein

the basic compound (E) is a triethanolamine compound.

<11> The positive resist composition as described in any one of <1> to<9>, wherein

the compound (B) is a compound represented by following formula (b-1) or(b-2):

wherein

each of Rb₁, Rb₂ and Rb₃ represents an alkyl group, a cycloalkyl group,or an aryl group, provided that at least one of Rb₁ to Rb₃ represents anaryl group;

Xb represents an alkylene fluoride group having from 2 to 6 carbonatoms; and

each of Yb and Zb independently represents an alkyl group.

<12> The positive resist composition as described in any one of <1> to<11>, further comprising:

at least one surfactant selected from a surfactant containing a fluorineatom, a surfactant containing a silicon atom, and a surfactantcontaining both a fluorine atom and a silicon atom.

<13> The positive resist composition as described in any one of <1> to<12>, wherein

the resin (C) is a solid at 25° C.

<14> The positive resist composition as described in any one of c< > to<13>, wherein

the resin (C) has a glass transition temperature of from 50 to 200° C.

<15> The positive resist composition as described in any one of <1> to<14>, wherein

the resin (C) has a weight average molecular weight of from 1,000 to50,000.

<16> The positive resist composition as described in any one of <1> to<15>, wherein

the resin (C) is contained in a proportion of from 0.1 to 5 mass % basedon all solids content in the positive resist composition.

<17> A pattern-forming method comprising:

forming a resist film with the resist composition as described in anyone of <1> to <16>;

exposing the formed resist film; and

developing the exposed film.

BRIEF DESCRIPTION OF THE DRAWING

FIGURE is an example of water mark defect.

DETAILED DESCRIPTION OF THE INVENTION

The invention will be described in detail below.

In the description of a group (an atomic group) in the specification ofthe invention, the description not referring to substitution orunsubstitution includes both a group not having a substituent and agroup having a substituent. For example, “an alkyl group” includes notonly an alkyl group having no substituent (an unsubstituted alkyl group)but also an alkyl group having a substituent (a substituted alkylgroup).

(A) A resin capable of increasing the solubility in an alkali developingsolution by the action of an acid:

A resin capable of increasing the solubility in an alkali developingsolution by the action of an acid (also referred to as resin (A)) foruse in the positive resist composition of the invention is athree-component type copolymer containing a (meth)acrylate unit (a1)having a lactone ring, a (meth)-acrylate unit (a2) having an organicgroup having a polar group, and a (meth)acrylate unit (a3) having anacid-decomposable group (an acid-dissociable dissolution-controllinggroup).

By containing a repeating unit (a1) derived from acrylic acid ormethacrylic acid ester having a lactone ring, adhesion with a substrateis improved, affinity with a developing solution is heightened, and filmpeeling can be restrained.

A repeating unit (a2) containing an organic group having a polar groupis specifically a constituting unit derived from acrylic acid ormethacrylic acid ester having a polar group-containing aliphatic oralicyclic hydrocarbon group. As the polar groups, a hydroxyl group, acyano group and an amino group can be exemplified, and a hydroxyl groupis preferred.

It is preferred for a repeating unit (a3) derived from anacid-decomposable group-containing acrylic acid or methacrylic acidester to have alicyclic group such as an adamantyl group, a norbornylgroup, a tetracyclodecanyl group, etc., for capable of giving a resistpattern of high resolution and excellent in etching resistance.

As the proportion of the contents of repeating units (a1), (a2) and(a3), a resist composition excellent in resolution can be obtained when(a1) is from 20 to 60 mol %, preferably from 20 to 50 mol %, and (a3) isfrom 30 to 60 mol %, preferably from 30 to 50 mol %. When the content ofthe constitutional unit (a2) is 50 mol % or less, preferably in therange of from 10 to 40 mol %, an excellent resist pattern can beobtained.

As the repeating units (a1), (a2) and (a3), bicycloalkane,tricycloalkane, or tetracycloalkane, e.g., repeating units having agroup formed by removing one or two or more hydrogen atoms fromadamantane, norbornane, isobornane, tricyclodecane, ortetracyclododecane, in particular, an adarnantyl group, a norbornylgroup, or a tetracyclodecanyl group are exemplified.

Resin (A) is specifically a resin containing repeating unit (a1)selected from repeating units represented by the following formulae(a1-1) to (a1-3), repeating unit (a2) represented by the followingformula (a-2), and repeating unit (a3) selected from repeating unitsrepresented by the following formulae (a3-1) to (a3-4), and capable ofincreasing the solubility in an alkali developing solution by the actionof an acid.

In the formulae, R represents a hydrogen atom, a halogen atom, or analkyl group; R′ represents an acid-decomposable group; each of R₁₂ andR₁₃ independently represents a hydrogen atom, a methyl group, an ethylgroup, or a propyl group; R₁₄ represents an alicyclic group; and nrepresents an integer of from 0 to 5.

The acid-decomposable group is a group capable of decomposing by theaction of an acid to generate an alkali-soluble group. A group preferredas the acid-decomposable group is a group obtained by substituting thehydrogen atom of an alkali-soluble group with a group capable ofelimination by the action of an acid.

The alkali-soluble groups include groups having a phenolic hydroxylgroup, a carboxylic acid group, a fluorinated alcohol group, a sulfonicacid group, a sulfonamido group, a sulfonylimido group, an(alkylsulfonyl)(alkylcarbonyl)-methylene group, an(alkylsulfonyl)(alkylcarbonyl)imido group, a bis(alkylcarbonyl)methylenegroup, a bis(alkyl-carbonyl)imido group, a bis(alkylsulfonyl)methylenegroup, a bis(alkylsulfonyl)imido group, a tris(alkylcarbonyl)-methylenegroup, or a tris(alkylsulfonyl)methylene group.

As the preferred alkali-soluble groups, a carboxylic acid group, afluorinated alcohol group (preferably hexafluoroisopropanol), and asulfonic acid group are exemplified.

As the group capable of elimination by the action of an acid,—C(R₃₆)(R₃₇)(R₃₈), —C(R₃₆)(R₃₇)(OR₃₉), —C(R₀₁)(R₀₂)(OR₃₉) and the likecan be exemplified.

In the formulae, R₃₆ to R₃₉ each represents an alkyl group, a cycloalkylgroup, an aryl group, an aralkyl group, or an alkenyl group. R₃₆ and R₃₇may be bonded to each other to form a ring.

R₀₁ and R₀₂ each represents a hydrogen atom, an alkyl group, acycloalkyl group, an aryl group, an aralkyl group, or an alkenyl group.

The preferred acid-decomposable groups are a cumyl ester group, an enolester group, an acetal ester group, a tertiary alkyl ester group, etc.,and the more preferred group is a tertiary alkyl ester group.

The alicyclic group is, to be more precise, an alicyclic hydrocarbongroup, which may be monocyclic or polycyclic. Specifically, groupshaving a monocyclic, bicyclic, tricyclic, or tetracyclic structurehaving 5 or more carbon atoms can be exemplified. The number of carbonatoms is preferably from 6 to 30, and especially preferably from 7 to25. These alicyclic hydrocarbon groups may have a substituent.

Of alicyclic hydrocarbon groups, the examples of the structures ofalicyclic parts are shown below.

In the invention, as the preferred of the above alicyclic parts, anadamantyl group, a noradamantyl group, a decalin residue, atricyclodecanyl group, a tetracyclododecanyl group, a norbornyl group, acedrol group, a cyclohexyl group, a cycloheptyl group, a cyclooctylgroup, a cyclodecanyl group, and a cyclododecanyl group can beexemplified. More preferred groups are an adamantyl group, a decalinresidue, a norbornyl group, a cedrol group, a cyclohexyl group, acycloheptyl group, a cyclooctyl group, a cyclodecanyl group, and acyclododecanyl group.

As the substituents of these alicyclic hydrocarbon groups, an alkylgroup, a halogen atom, a hydroxyl group, an alkoxyl group, a carboxylgroup, and an alkoxycarbonyl group are exemplified. As the alkyl group,lower alkyl groups such as a methyl group, an ethyl group, a propylgroup, an isopropyl group and a butyl group are preferred, and a methylgroup, an ethyl group, a propyl group, and an isopropyl group are morepreferred. As the alkoxyl group, those having from 1 to 4 carbon atoms,e.g., a methoxy group, an ethoxy group, a propoxy group and a butoxygroup can be exemplified. The alkyl group and alkoxyl group may furtherhave a substituent. As the further substituents of the alkyl group andalkoxyl group, a hydroxyl group, a halogen atom and an alkoxyl group areexemplified.

It is preferred for resin (A) to further contain repeating unit (a4)having any structure selected from the following (a4-1) to (a4-3).

In the formulae, R represents a hydrogen atom, a halogen atom, or analkyl group.

Resin (A) can contain various repeating structural units besides theabove repeating structural units for the purpose of the adjustments ofdry etching resistance, aptitude for standard developing solutions,adhesion to a substrate, resist profile, and further, general requisitecharacteristics of the resist, e.g., resolution, beat resistance andsensitivity.

As these repeating structural units, the repeating structural unitscorresponding to the monomers shown below can be exemplified, but theinvention is not restricted thereto.

By containing such repeating structural units, fine adjustment ofperformances required of the resin of component (A), in particular thefollowing performances, becomes possible, that is,

(1) Solubility in a coating solvent,(2) A film-forming property (a glass transition point),(3) An alkali developing property,(4) Decrease of layer thickness (hydrophobic-hydrophilic property,selection of an alkali-soluble group),(5) Adhesion of an unexposed part to a substrate, and(6) Dry etching resistance.

The examples of such monomers include compounds having one additionpolymerizable unsaturated bond selected from acrylic acid esters,methacrylic acid esters, acrylamides, methacrylamides, allyl compounds,vinyl ethers, vinyl esters, etc.

In addition to the aforementioned compounds, addition polymerizableunsaturated compounds copolymerizable with the monomers corresponding tothe above various repeating structural units may be used forcopolymerization.

In the resin of component (A), the molar ratio of the content of eachrepeating structural unit is arbitrarily set to adjust dry etchingresistance and aptitude for standard developing solutions of a resist,adhesion to a substrate, and resist profile, further, general requisitecharacteristics of a resist, e.g., resolution, heat resistance andsensitivity.

When the positive resist composition of the invention is for ArFexposure, it is preferred that the resin of component (A) does not havean aromatic group from the aspect of the transparency to ArF rays.

The resin of component (A) is preferably such that all the repeatingunits consist of (meth)acrylate repeating units. In this case, any ofthe following cases can be used, that is, a case where all the repeatingunits consist of methacrylate repeating units, a case where all therepeating units consist of acrylate repeating units, and a case whereall the repeating units consist of methacrylate repeating units andacrylate repeating units, but it is preferred that acrylate repeatingunits account for 50 mol % or less of all the repeating units. Morepreferred resins are copolymers comprising from 20 to 50 mol % of(meth)acrylate repeating units having an acid-decomposable group, from20 to 50 mol % of (meth)acrylate repeating units having a lactonestructure, from 5 to 30 mol % of (meth)acrylate repeating units havingan alicyclic hydrocarbon structure substituted with a hydroxyl group ora cyano group, and further containing from 0 to 20 mol % of other(meth)acrylate repeating units.

The resin of component (A) can be synthesized according to ordinarymethods (for example, radical polymerization). For example, as ordinarysynthesizing methods, a batch polymerization method of dissolving amonomer seed and an initiator in a solvent and heating the solution toperform polymerization, and a dropping polymerization method of adding asolution of a monomer seed and an initiator to a heated solvent over 1to 10 hours by dropping are exemplified, and the dropping polymerizationmethod is preferred. As reaction solvents, ethers, e.g.,tetrahydrofuran, 1,4-dioxane, diisopropyl ether, etc., ketones, e.g.,methyl ethyl ketone, methyl isobutyl ketone, etc., ester solvents, e.g.,ethyl acetate, amide solvents, e.g., dimethylformamide anddimethyacetamide, and the later-described solvents capable of dissolvingthe composition of the invention, e.g., propylene glycol monomethylether acetate, propylene glycol monomethyl ether, and cyclohexanone areexemplified. It is more preferred to use the same solvent in thepolymerization as the solvent used in the positive resist composition ofthe invention, by which the generation of particles during preservationcan be restrained.

It is preferred to perform the polymerization reaction in the atmosphereof inert gas such as nitrogen or argon. Polymerization is initiated withcommercially available radical polymerization initiators (e.g., azoinitiators, peroxide and the like). As radical polymerizationinitiators, azo initiators are preferred, and azo initiators having anester group, a cyano group, or a carboxyl group are preferred. Aspreferred initiators, azobisisobutyronitrile,azobis-dimethylvaleronitrile, dimethyl-2,2′-azobis(2-methyl-propionate),etc., are exemplified. Initiators are added additionally or dividedly,if desired, and after termination of the reaction, the reaction productis put into a solvent and an objective polymer is recovered as powder orin a solid state. The reaction concentration is from 5 to 50 mass %, andpreferably from 10 to 30 mass %. The reaction temperature is generallyfrom 11 to 150° C., preferably from 30 to 120° C., and more preferablyfrom 60 to 100° C.

The weight average molecular weight of the resin of component (A) ispreferably from 1,000 to 200,000 as the polystyrene equivalent by theGPC method, more preferably from 3,000 to 20,000, and most preferablyfrom 5,000 to 15,000. By making the weight average molecular weight from1,000 to 200,000, deteriorations of heat resistance and dry etchingresistance can be prevented, and degradations of developing property andfilm-forming property due to increase in viscosity can be prevented.

The degree of dispersion (molecular weight distribution) of the resin ofcomponent (A) is generally from 1 to 5, preferably from 1 to 3, and morepreferably from 1 to 2. The smaller the molecular weight distribution,the more excellent is the resin in resolution and the resist form, andthe more smooth is the sidewall of the resist pattern, and the moreexcellent is the roughness property.

When resin (A) contains repeating unit (a4), the content of therepeating unit (a4) in resin (A) is preferably from 0.5 to 20 mol %, andmore preferably from 1 to 10 mol %.

A plurality of kinds of repeating units (a1) to (a4) may be containedrespectively.

In the positive resist composition of the invention, the blending amountof the resin of component (A) in the composition at large is preferablyfrom 50 to 99.99 mass % based on all the solids content, and morepreferably from 60 to 99.0 mass %.

In the invention, the resin of component (A) may be used by one kindalone, or two or more kinds of resins may be used in combination.

(B) A compound capable of generating an acid upon irradiation withactinic ray or radiation:

The photosensitive composition of the invention contains a compoundcapable of generating an acid upon irradiation with actinic ray orradiation (also referred to as component (B) or compound (B)).

As such light-acid generators, photoinitiators of photocationicpolymerization, photoinitiators of photoradical polymerization,photo-decoloring agents and photo-discoloring agents of dyestuffs, andwell-known compounds capable of generating an acid upon irradiation withactinic ray or radiation that are used in micro-resists, and mixtures ofthese compounds can be optionally selected and used.

For example, diazonium salt, phosphonium salt sulfonium salt, iodoniumsalt, imidosulfonate, oximesulfonate, diazodisulfone, disulfone, ando-nitrobenzylsulfonate are exemplified.

Further, compounds obtained by introducing a group or a compound capableof generating an acid upon irradiation with actinic ray or radiationinto the main chain or side chain of polymers, for example, thecompounds disclosed in U.S. Pat. No. 3,849,137, German Patent 3,914,407,JP-A-63-26653, JP-A-55-164824, JP-A-62-69263, JP-A-63-146038,JP-A-63-163452, JP-A-62-153853, JP-A-63-146029, etc., can be used.

The compounds capable of generating an acid by the action of lights asdisclosed in U.S. Pat. No. 3,779,778, EP 126,712, etc., can also beused.

Component (B) is preferably a compound capable of generating an acidhaving a fluoroalkyl chain (preferably having from 2 to 4 carbon atoms)or a benzenesulfonic acid having a fluorine atom upon irradiation withactinic ray.

Component (B) is also preferably a triphenylsulfonium salt compoundhaving, at the cationic part, an alkyl residue (preferably having from 1to 15 carbon atoms) not substituted with a fluorine atom or a cycloalkylresidue (preferably having from 3 to 15 carbon atoms) not substitutedwith a fluorine atom.

Of the compounds capable of decomposing upon irradiation with actinicray or radiation and generating an acid, the compounds represented byany of the following formulae (ZI), (ZII) and (ZIII) can be exemplifiedas preferred compounds.

In formula (ZI), R₂₀₁, R₂₀₂ and R₂₀₃ each represents an organic group.

X⁻ represents a non-nucleophilic anion, preferably a sulfonate anion, acarboxylate anion, a bis(alkylsulfonyl)-amide anion, atris(alkylsulfonyl)methide anion, F₄ ⁻; PF₆ ⁻, SbF₆ ⁻, etc., areexemplified, and preferably an organic anion containing a carbon atom.

As preferred organic anions, organic anions represented by the followingformulae are exemplified.

In the above formulae, Rc₁ represents an organic group.

As the organic group represented by Rc₁, an organic group having from 1to 30 carbon atoms is exemplified, preferably an alkyl group, an arylgroup, each of which groups may be substituted, and a group obtained bylinking a plurality of these groups with a linking group such as asingle bond, —O—, —CO₂—, —S—, —SO₃— or —SO₂N(Rd₁)— can be exemplified.Rd₁ represents a hydrogen atom or an alkyl group.

Rc₃, Rc₄ and Rc₅ each represents an organic group. As preferred organicgroups represented by Rc₃, Rc₄ and Rc₅, the same organic groups as thepreferred organic groups in Rc₁ can be exemplified, and a perfluoroalkylgroup having from 1 to 4 carbon atoms is most preferred.

Rc₃ and Rc₄ may be bonded to each other to form a ring.

As the group formed by bonding Rc₃ and Rc₄, an alkylene group and anarylene group are exemplified, and a perfluoro-alkylene group havingfrom 2 to 4 carbon atoms is preferred.

The especially preferred organic groups represented by Rc₁, Rc₃ to Rc₅are an alkyl group substituted with a fluorine atom or a fluoroalkylgroup on the 1-position, and a phenyl group substituted with a fluorineatom or a fluoroalkyl group. By the presence of a fluorine atom or afluoroalkyl group, the acidity of the acid generated upon lightirradiation increases to enhance sensitivity. Further, by the presenceof a ring formed by bonding Rc₃ and Rc₄, the acidity of the acidgenerated upon light irradiation increases to improve sensitivity.

The number of carbon atoms of the organic groups represented by R₂₀₁,R₂₀₂ and R₂₀₃ is generally from 1 to 30, and preferably from 1 to 20.

Any two of R₂₀₁, R₂₀₂ and R₂₀₃ may be bonded to each other to form acyclic structure, and an oxygen atom, a sulfur atom, an ester bond, anamido bond or a carbonyl group may be contained in the ring.

As the group formed by any two of R₂₀₁, R₂₀₂ and R₂₀₃ by bonding, analkylene group (e.g., a butylene group and a pentylene group) can beexemplified.

As the specific examples of the organic groups represented by R₂₀₁, R₂₀₂and R₂₀₃, the corresponding groups in compounds (ZI-1), (ZI-2) and(ZI-3) described later can be exemplified.

The compound represented by formula (ZI) may be a compound having aplurality of structures represented by formula (ZI). For instance,compound (ZI) may be a compound having a structure that at least one ofR₂₀₁, R₂₀₂ and R₂₀₃ of the compound represented by formula (ZI) isbonded to at least one of R₂₀₁, R₂₀₂ and R₂₀₃ of another compoundrepresented by formula (ZI).

As further preferred component (ZI), the following compounds (ZI-1),(ZI-2) and (ZI-3) can be exemplified.

Compound (ZI-1) is an arylsulfonium compound in the case where at leastone of R₂₀₁, R₂₀₂ and R₂₀₃ in formula (ZI) represents an aryl group,that is, a compound having arylsulfonium as the cation,

All of R₂₀₁, R₂₀₂ and R₂₀₃ of the arylsulfonium compound may be arylgroups, or a part of R₂₀₁, R₂₀₂ and R₂₀₃ may be an aryl group and theremainder may be an alkyl group.

As the arylsulfonium compound, e.g., a triarylsulfonium compound, adiarylalkylsulfonium compound, and an aryl-dialkylsulfonium compound canbe exemplified.

As the aryl group of the arylsulfonium compound, an aryl group, e.g., aphenyl group and a naphthyl group, and a hetero-aryl group, e.g., anindole residue and a pyrrole residue are preferred, and a phenyl groupand an indole residue are more preferred. When the arylsulfoniumcompound has two or more aryl groups, these two or more aryl groups maybe the same or different.

The alkyl group introduced into the arylsulfonium compound according tonecessity is preferably a straight chain, branched, or cyclic alkylgroup having from 1 to 15 carbon atoms, e.g., a methyl group, an ethylgroup, a propyl group, an n-butyl group, a sec-butyl group, a t-butylgroup, a cyclopropyl group, a cyclobutyl group, a cyclohexyl group,etc., can be exemplified.

The aryl group and alkyl group represented by R₂₀₁, R₂₀₂ and R₂₀₃ mayhave a substituent, e.g., an alkyl group (e.g., having from 1 to 15carbon atoms), an aryl group (e.g., having from 6 to 14 carbon atoms),an alkoxyl group (e.g., having from 1 to 15 carbon atoms), a halogenatom, a hydroxyl group, and a phenylthio group are exemplified as thesubstituents. The preferred substituents are a straight chain, branched,or cyclic alkyl group having from 1 to 12 carbon atoms, and a straightchain, branched or cyclic alkoxyl group having from 1 to 12 carbonatoms, and the most preferred substituents are an alkyl group havingfrom 1 to 4 carbon atoms, and an alkoxyl group having from 1 to 4 carbonatoms. The substituent may be substituted on any one of three of R₂₀₁,R₂₀₂ and R₂₀₃, or may be substituted on all of the three. When R₂₀₁,R₂₀₂ and R₂₀₃ each represents an aryl group, it is preferred that thesubstituent is substituted on the p-position of the aryl group.

Compound (ZI-2) is described below.

Compound (ZI-2) is a compound in the case where R₂₀₁, R₂₀₂ and R₂₀₃ informula (ZI) each represents an organic group not having an aromaticring. The aromatic ring here also includes an aromatic ring containing ahetero atom.

The organic group not having an aromatic ring represented by R₂₀₁, R₂₀₂and R₂₀₃ generally has from 1 to 30 carbon atoms, and preferably from 1to 20 carbon atoms.

R₂₀₁, R₂₀₂ and R₂₀₃ each preferably represents an alkyl group, a2-oxoalkyl group, an alkoxycarbonylmethyl group, an allyl group, or avinyl group, more preferably represents a straight chain, branched, orcyclic 2-oxoalkyl group, or an alkoxycarbonylmethyl group, and mostpreferably a straight chain or branched 2-oxoalkyl group.

The alkyl group represented by R₂₀₁, R₂₀₂ and R₂₀₃ may be any ofstraight chain, branched, and cyclic, preferably a straight chain orbranched alkyl group having from 1 to 10 carbon atoms (e.g., a methylgroup, an ethyl group, a propyl group, a butyl group, and a pentylgroup), and a cyclic alkyl group having from 3 to 10 carbon atoms (e.g.,a cyclopentyl group, a cyclohexyl group, and a norbonyl group) can beexemplified.

The 2-oxoalkyl group represented by R₂₀₁, R₂₀₂ and R₂₀₃ may be any ofstraight chain, branched, and cyclic, and preferably groups having >C═Oon the 2-position of the above alkyl groups can be exemplified.

As the alkoxyl group in the alkoxycarbonylmethyl group represented byR₂₀₁, R₂₀₂ and R₂₀₃, preferably an alkoxy group having from 1 to 5carbon atoms, e.g., a methoxy group, an ethoxy group, a propoxy group, abutoxy group, a pentoxy group can be exemplified.

R₂₀₁, R₂₀₂ and R₂₀₃ may further be substituted with a halogen atom, analkoxyl group (e.g., having from 1 to 5 carbon atoms), a hydroxyl group,a cyano group, or a nitro group.

Any two of R₂₀₁, R₂₀₂ and R₂₀₃ may be bonded to each other to form acyclic structure, and an oxygen atom, a sulfur atom, an ester bond, anamido bond or a carbonyl group may be contained in the ring. As thegroup formed by any two of R₂₀₁, R₂₀₂ and R₂₀₃ by bonding, an alkylenegroup (e.g., a butylene group and a pentylene group) can be exemplified.

Compound (ZI-3) is a compound represented by the following formula(ZI-3) and having a phenacylsulfonium salt structure.

R_(1c), R_(2c), R_(3c), R_(4c) and R_(5c) each represents a hydrogenatom, an alkyl group, an alkoxyl group, or a halogen atom.

R_(6c) and R_(7c) each represents a hydrogen atom or an alkyl group.

R_(x) and R_(y) each represents an alkyl group, a 2-oxoalkyl group, analkoxycarbonylmethyl group, an allyl group, or a vinyl group.

Any two or more of R_(1c), to R_(5c), and R_(x), and R_(y) may be bondedto each other to form cyclic structures, respectively, and the cyclicstructures may contain an oxygen atom, a sulfur atom, an ester bond, oran amido bond.

The alkyl group represented by R_(1c) to R_(5c) may be any of straightchain, branched, and cyclic, e.g., an alkyl group having from 1 to 20carbon atoms, preferably a straight chain or branched alkyl group havingfrom 1 to 12 carbon atoms (e.g., a methyl group, an ethyl group, astraight chain or branched propyl group, a straight chain or branchedbutyl group, and a straight chain or branched pentyl group), and acyclic alkyl group having from 3 to 8 carbon atoms (e.g., a cyclopentylgroup and a cyclohexyl group) can be exemplified.

The alkoxyl group represented by R_(1c) to R_(5c) may be any of straightchain, branched, and cyclic, e.g., an alkoxyl group having from 1 to 10carbon atoms, preferably a straight chain or branched alkoxyl grouphaving from 1 to 5 carbon atoms (e.g., a methoxy group, an ethoxy group,a straight chain or branched propoxy group, a straight chain or branchedbutoxy group, and a straight chain or branched pentoxy group), a cyclicalkoxyl group having from 3 to 8 carbon atoms (e.g., a cyclopentyloxygroup, and a cyclohexyloxy group) can be exemplified.

It is preferred that any of R_(1c) to R_(5c) represents a straightchain, branched, or cyclic alkyl group, or a straight chain, branched,or cyclic alkoxyl group, and more preferably the sum total of the carbonatoms of R_(1c) to R_(5c) is from 2 to 15, by which the solubility in asolvent is bettered and the generation of particles during preservationcan be restrained.

As the alkyl group represented by R_(x) and R_(y), the same alkyl groupsrepresented by R_(1c) to R_(5c) can be exemplified.

As the 2-oxoalkyl group, groups having >C═O on the 2-position of thealkyl groups represented by R_(1c) to R_(5c) can be exemplified.

As the alkoxyl group of the alkoxycarbonylmethyl group, the same alkoxylgroups as those represented by R_(1c) to R_(5c) can be exemplified.

As the groups formed by R_(x) and R_(y) by bonding, a butylene group, apentylene group, etc., can be exemplified.

R_(x) and R_(y) each preferably represents an alkyl group having 4 ormore carbon atoms, more preferably 6 or more carbon atoms, and stillmore preferably an alkyl group having 8 or more carbon atoms.

In formulae (ZII) and (ZIII), R₂₀₄, R₂₀₅, R₂₀₆ and R₂₀₇ each representsan aryl group that may have a substituent, or an alkyl group that mayhave a substituent.

The aryl group represented by R₂₀₄ to R₂₀₇ is preferably a phenyl groupor a naphthyl group, and more preferably a phenyl group.

The alkyl group represented by R₂₀₄ to R₂₀₇ may be any of straightchain, branched, and cyclic, and preferably a straight chain or branchedalkyl group having from 1 to 10 carbon atoms (e.g., a methyl group, anethyl group, a propyl group, a butyl group, and a pentyl group), and acyclic alkyl group having from 3 to 10 carbon atoms (e.g., a cyclopentylgroup, a cyclohexyl group, a norbornyl group) can be exemplified.

As the examples of the substituents that R₂₀₄ to R₂₀₇ may have, e.g., analkyl group (e.g., having from 1 to 15 carbon atoms), an aryl group(e.g., having from 6 to 15 carbon atoms), an alkoxyl group (e.g., havingfrom 1 to 15 carbon atoms), a halogen atom, a hydroxyl group, aphenylthio group, etc., can be exemplified.

X⁻ represents a non-nucleophilic anion, and the same anions as thenon-nucleophilic anion represented by X⁻ in formula (ZI) can beexemplified.

Of the compounds capable of generating an acid upon irradiation withactinic ray or radiation that may be used in combination, the compoundsrepresented by the following formula (ZIV), (ZV) or (ZVI) can further beexemplified as preferred compounds.

In formulae (ZIV) to (ZVI), Ar₃ and Ar₄ each represents an aryl group.

R₂₀₆ represents an alkyl group or a substituted or unsubstituted arylgroup.

R₂₀₇ and R₂₀₈ each represents an alkyl group, an aryl group, or anelectron attractive group. R₂₀₇ preferably represents an aryl group.

R₂₀₈ preferably represents an electron attractive group, and morepreferably a cyano group or a fluoroalkyl group.

A represents an alkylene group, an alkenylene group, or an arylenegroup.

Of the compounds capable of decomposing upon irradiation with actinicray or radiation and generating an acid, the compounds represented byany of formulae (ZI), (ZII) and (ZIII) are more preferred.

As acid generators, the compounds represented by the following formula(b-1) or (b-2) are also preferably used.

In formulae (b-1) and (b-2), each of Rb₁, Rb₂ and Rb₃ represents analkyl group, a cycloalkyl group, or an aryl group, provided that atleast one of Rb₁ to Rb₃ represents an aryl group.

Xb represents an alkylene fluoride group having from 2 to 6 carbonatoms.

each of Yb and Zb independently represents an alkyl group.

The alkyl group represented by Rb₁ to Rb₃ is an alkyl group having from1 to 6 carbon atoms, preferably an alkyl group having from 1 to 4 carbonatoms, and the cycloalkyl group is preferably a cycloalkyl group havingfrom 3 to 10 carbon atoms, and more preferably from 4 to 6 carbon atoms.

As the alkylene fluoride group having from 2 to 6 carbon atomsrepresented by Xb, a perfluoroalkylene group is especially preferred.

As the alkyl group represented by Yb and Zb, an alkyl fluoride group ispreferred, and the one having from 1 to 6 carbon atoms is preferred, andmore preferably the one having from 1 to 4 carbon atoms.

Of the compounds capable of generating an acid upon irradiation withactinic ray or radiation, the examples of especially preferred compoundsare shown below.

The acid generators can be used by one kind alone, or two or more kindscan be used in combination. When two or more compounds are used incombination, it is preferred to combine compounds capable of generatingtwo kinds of organic acids in which the total atom number exclusive of ahydrogen atom differs by 2 or more. The content of the acid generator ina composition is preferably from 0.1 to 20 mass % based on all thesolids content of the resist composition, more preferably from 0.5 to 10mass %, and still more preferably from 1 to 7 mass %.

(C) A resin containing at least one of a fluorine atom and a siliconatom

The positive resist composition of the invention contains a resin(hereinafter also referred to as resin (C)) containing at least one of afluorine atom and a silicon atom, and a group selected from thefollowing groups (x) to (z):

(x) an alkali-soluble group,

(y) a group capable of decomposing by the action of an alkali developingsolution to increase the solubility in the alkali developing solution,and

(z) a group capable of decomposing by the action of an acid.

As alkali-soluble group (x), groups having a phenolic hydroxyl group, acarboxylic acid group, a fluorinated alcohol group, a sulfonic acidgroup, a sulfonamido group, a sulfonylimido group, an(alkylsulfonyl)(alkylcarbonyl)-methylene group, an(alkylsulfonyl)(alkylcarbonyl)imido group, a bis(alkylcarbonyl)methylenegroup, a bis(alkyl-carbonyl)imido group, a bis(alkylsulfonyl)methylenegroup, a bis(alkylsulfonyl)imido group, a tris(alkylcarbonyl)-methylenegroup, and a tris(alkylsulfonyl)methylene group are exemplified.

As the preferred alkali-soluble groups, a fluorinated alcohol group(preferably hexafluoroisopropanol), a sulfonamido group, and abis(carbonyl)methylene group are exemplified.

As the repeating unit having alkali-soluble group (x), all of arepeating unit in which an alkali-soluble group is directly bonded tothe main chain of a resin, such as a repeating unit by an acrylic acidor a methacrylic acid, a repeating unit in which an alkali-soluble groupis bonded to the main chain of a resin via a linking group, and arepeating unit obtained by introducing an alkali-soluble group by usinga polymerization initiator or a chain transfer agent having analkali-soluble group to the terminal of a polymer chain at the time ofpolymerization are preferably used.

The content of the repeating unit having alkali-soluble group (x) ispreferably from 1 to 50 mol % to all the repeating units in the polymer,more preferably from 3 to 35 mol %, and still more preferably from 5 to20 mol %.

The specific examples of the repeating units having alkali-soluble group(x) are shown below. In the formulae, Rx represents H, CH₃, CF₃ orCH₂OH.

As group (y) capable of decomposing by the action of an alkalideveloping solution to increase the solubility in the alkali developingsolution, e.g., a group having a lactone structure, an acid anhydride,an acid imido group, etc., are exemplified, and a lactone group ispreferred.

As the repeating unit having group (y) capable of decomposing by theaction of an alkali developing solution to increase the solubility inthe alkali developing solution, any of a repeating unit in which analkali-soluble group is bonded to the main chain of a resin via alinking group, such as a repeating unit by an acrylic acid ester or amethacrylic acid ester, and a repeating unit obtained by introducinggroup (y) capable of increasing the solubility in an alkali developingsolution by using a polymerization initiator or a chain transfer agenthaving group (y) to the terminal of a polymer chain at the time ofpolymerization are preferably used.

The content of the repeating unit having group (y) capable of increasingthe solubility in an alkali developing solution is preferably from 1 to40 mol % to all the repeating units in the polymer, more preferably from3 to 30 mol %, and still more preferably from 5 to 15 mol %.

As the specific examples of the repeating units having group (y) capableof increasing the solubility in an alkali developing solution, thefollowing lactone structures, and a structure represented by formula(VIII) are exemplified.

It is preferred for resin (C) in the invention to have a group having alactone ring. As the group having a lactone ring, any group can be usedso long as the group has a lactone ring, but groups having a 5- to7-membered ring lactone structure are preferred, and groups having a 5-to 7-membered ring lactone structure condensed with other ringstructures in the form of forming a bicyclo structure or a spirostructure are preferred. Groups having a lactone structure representedby any of the following formulae (LC1-1) to (LC1-16) are more preferred.A group having a lactone structure may be directly bonded to the mainchain of a repeating unit. Preferred lactone structures are groupsrepresented by (LC1-1), (LC1-4), (LC1-5), (LC1-6), (LC1-13) and(LC1-14).

A lactone structure moiety may have or may not have a substituent (Rb₂).As preferred substituent (Rb₂), an alkyl group having from 1 to 8 carbonatoms, a cycloalkyl group having from 4 to 7 carbon atoms, an alkoxylgroup having from 1 to 8 carbon atoms, an alkoxycarbonyl group havingfrom 1 to 8 carbon atoms, a carboxyl group, a halogen atom, a hydroxylgroup, a cyano group, and an acid-decomposable group are exemplified. n₂represents an integer of from 0 to 4. When n₂ is 2 or more, a pluralityof Rb₂'s may be the same or different, and a plurality of Rb₂'s may bebonded to each other to form a ring.

As the repeating unit having a group having a lactone structurerepresented by any of formulae (LC1-1) to (LC1-16), for example, arepeating unit represented by the following formula (AI) can beexemplified.

In formula (AI), Rb₀ represents a hydrogen atom, a halogen atom, or analkyl group having from 1 to 4 carbon atoms. As the preferredsubstituents that the alkyl group represented by Rb₀ may have, ahydroxyl group and a halogen atom are exemplified.

As the halogen atom represented by Rb₀, a fluorine atom, a chlorineatom, a bromine atom and an iodine atom can be exemplified. Rb₀preferably represents a hydrogen atom or a methyl group.

Ab represents an alkylene group, a divalent linking group having amonocyclic or polycyclic alicyclic hydrocarbon structure, a single bond,an ether group, an ester group, a carbonyl group, a carboxyl group, or adivalent linking group combining these groups. Ab preferably representsa single bond or a linking group represented by -Ab₁-CO₂—.

Ab₁ represents a straight chain or branched alkylene group, or amonocyclic or polycyclic cycloalkylene group, and preferably a methylenegroup, an ethylene group, a cyclohexylene group, an adamantylene group,or a norbornylene group.

V represents a group represented by any of formulae (LC1-1) to (LC1-16).

Repeating units having a lactone structure generally have opticalisomers, and any optical isomer may be used. One kind of optical isomermay be used alone, or a plurality of optical isomers may be used asmixture. When one kind of optical isomer is mainly used, the opticalpurity (ee) of the optical isomer is preferably 90 or more, and morepreferably 95 or more.

The specific examples of the repeating units having a group having alactone structure are shown below, but the invention is not restrictedthereto.

(In the formulae, Rx represents H, CH₃, CH₂OH or CF₃.)

(In the formulae, Rx represents H, CH₃, CH₂OH or CF₃.)

(In the formulae, Rx represents H, CH₃, CH₂OH or CF₃.)

In formula (VIII), Z₂ represents —O— or —N(R₄₁)—. R₄₁ represents ahydrogen atom, a hydroxyl group, an alkyl group, or —OSO₂—R₄₂. R₄₂represents an alkyl group, a cycloalkyl group, or a camphor residue. Thealkyl group represented by R₄₁ and R₄₂ may be substituted with a halogenatom (preferably a fluorine atom) and the like.

As the specific examples of the repeating units represented by formula(VIII), the following compounds are exemplified, but the invention isnot restricted thereto.

Group (z) capable of decomposing by the action of an acid (anacid-decomposable group) is preferably a group obtained by substitutingthe hydrogen atom of an alkali-soluble group such as a —COOH group or an—OH group with a group capable of elimination by the action of an acid.

As the group capable of elimination by the action of an acid,—C(R₃₆)(R₃₇)(R₃₈), —C(R₃₆)(R₃₇)(OR₃₉), —C(R₀₁)(R₀₂)(OR₃₉) and the likecan be exemplified.

In the formulae, R₃₆ to R₃₉ each represents an all group, a cycloalkylgroup, an aryl group, an aralkyl group, or an alkenyl group. R₃₆ andR₃₇, and R₃₆ and R₃₉ may be bonded to each other to form a ring.

R₀₁ and R₀₂ each represents a hydrogen atom, an alkyl group, acycloalkyl group, an aryl group, an aralkyl group, or an alkenyl group.

In the invention, the acid-decomposable group is preferably an acetalgroup or a tertiary ester group.

The content of the repeating unit having group (z) capable ofdecomposing by the action of an acid of resin (C) is preferably from 1to 80 mol % to all the repeating units in the polymer, more preferablyfrom 10 to 80 mol %, and still more preferably from 20 to 60 mol %.

By containing resin (C) in the resist composition of the invention,resin (C) is locally present on the surface layer of the photosensitivefilm, and when the immersion medium is water, the resist composition asformed to a photosensitive film can improve the sweepback contact angleof the surface layer of the photosensitive film to water, and canimprove the following ability of immersion liquid. Resins as resin (C)are not restricted so long as the sweepback contact angle of the surfacelayer is improved by the addition, but resins having at least either afluorine atom or a silicon atom are preferably used. The sweepbackcontact angle of a photosensitive film is preferably from 60 to 90°, andmore preferably 70° or more.

The addition amount of resin (C) can be arbitrarily selected so as toreach the above range of the sweepback contact angle of thephotosensitive film. The addition amount is preferably from 0.1 to 10mass % based on all the solids content of the photosensitivecomposition, and more preferably from 0.1 to 5 mass %.

As described above, resin (C) is present locally on the interface, butdiffering from surfactants, it does not necessarily have to have ahydrophilic group in the molecule and contribute to homogeneous blendingof polar and nonpolar substances.

Resin (C) is preferably an alkali-soluble resin containing an alkylgroup having a fluorine atom and from 1 to 4 carbon atoms, a cycloalkylgroup having a fluorine atom, or an aryl group having a fluorine atom.

Resin (C) preferably contains an alcoholic hydroxyl groups and thealcohol moiety of the alcoholic hydroxyl group is a fluorinated alcohol.

It is preferred that resin (C) is at least either resin (C1) having atleast a fluorine atom or a silicon atom, and an alicyclic structure, orresin (C2) containing a repeating unit having at least a fluorine atomor a silicon atom on the side chain, and a repeating unit having anunsubstituted alkyl group on the side chain.

Resin (C) is preferably a hydrophobic resin (HP). Hydrophobic resin (HP)can also be preferably used as a topcoat.

A fluorine atom or a silicon atom in a hydrophobic resin (HP) may beintroduced to the main chain of the resin or may be substituted on theside chain.

“A hydrophobic resin” is a resin capable of contribution to theimprovement of the contact angle to water of the surface of aphotosensitive film by the addition to die photosensitive film.

Hydrophobic resins are not restricted so long as the resins are capableof improving the sweepback contact angle of the surface of a film byaddition, but they are preferably resins having at least either afluorine atom or a silicon atom. When applied to immersion exposure, itis preferred that the sweepforward contact angle of the photosensitivefilm is adjusted to 70° to 120°, and more preferably from 75° to 100°,The sweepback contact angle is preferably adjusted to 60° to 100°, andmore preferably from 70° to 90°. The addition amount of a hydrophobicresin (HP) can be arbitrarily adjusted so that the sweepback contactangle of a photosensitive film reaches the above range, but it ispreferably from 0.1 to 10 mass % based on all the solids content of thephotosensitive composition, and more preferably from 0.1 to 5 mass %.

It is preferred that sweepback contact angle can be improved with asmaller addition amount, so that the glass transition point (Tg) ofhydrophobic resins is preferably in the range of from 50 to 200° C.

Hydrophobic resins axe preferably solid at normal temperature (25° C.).

The sweepforward contact angle and sweepback contact angle defined hereare sweepforward and sweepback contact angles measured according to anextraction contraction method. Specifically, a droplet of 36 μL isformed with a syringe on a positive resist composition prepared on asilicon wafer, and the droplet is ejected or sucked at a speed of 6μl/sec, and the values stabilized during ejection and suction aredefined as the sweepforward and sweepback contact angles.

Many hydrophobic resins are present locally on the interface, butdiffering from surfactants, they do not necessarily have to have ahydrophilic group in the molecule and contribute to homogeneous blendingof polar and nonpolar substances.

“Soluble in an alkali developing solution” means that the dissolvedamount of a hydrophobic resin film in a 2.38 wt % tetramethylammoniumhydroxide aqueous solution at 23° C. is 50 nm or more as integration for30 seconds from the start of development. In order to be soluble in analkali developing solution, it is necessary for a photosensitive resinfilm to have an alkali-soluble group in a developing process.

Hydrophobic resins may have an alkali-soluble group in advance, or analkali-soluble group may be formed by the action of an acid during theprocesses of from exposure to development, or it may be formed byreaction with an alkali developing solution.

Resin (HP) is preferably a resin having an alkyl group having a fluorineatom, a cycloalkyl group having a fluorine atom, or an aryl group havinga fluorine atom, as the partial structure having a fluorine atom.

The alkyl group having a fluorine atom (preferably having from 1 to 10carbon atoms, and more preferably from 1 to 4 carbon atoms) is astraight chain or branched alkyl group in which at least one hydrogenatom is substituted with a fluorine atom, and the group may further haveother substituents.

The cycloalkyl group having a fluorine atom is a monocyclic orpolycyclic cycloalkyl group in which at least one hydrogen atom issubstituted with a fluorine atom, and the group may further have othersubstituents.

The aryl group having a fluorine atom is an aryl group such as a phenylgroup or a naphthyl group in which at least one hydrogen atom issubstituted with a fluorine atom, and the group may further have othersubstituents.

General formulae of the alkyl group having a fluorine atom, thecycloalkyl group having a fluorine atom, and the aryl group having afluorine atom respectively are shown below, but the invention is notrestricted thereto.

In formulae (F2) to (F4), R₅₇ to R₆₈ each represents a hydrogen atom, afluorine atom, or an alkyl group. However, at least one of R₅₇ to R₆₁,R₆₂ to R₆₄, and R₆₅, to R₆₈, respectively represent a fluorine atom, oran alkyl group (preferably having from 1 to 4 carbon atoms) in which atleast one hydrogen atom is substituted with a fluorine atom. It ispreferred that all of R₅₇ to R₆₁ and R₆₅ to R₆₇ represent a fluorineatom. R₆₂, R₆₃ and R₆₈ each preferably represents an alkyl group(preferably having from 1 to 4 carbon atoms) in which at least onehydrogen atom is substituted with a fluorine atom, and more preferably aperfluoroalkyl group having from 1 to 4 carbon atoms. R₆₂ and R₆₃ may belinked to each other to form a ring.

As the specific examples of the groups represented by formula (F2), ap-fluorophenyl group, a pentafluorophenyl group, a3,5-di(trifluoromethyl)phenyl group, etc., are exemplified.

The specific examples of the groups represented by formula (F3) includea trifluoromethyl group, a pentafluoro-propyl group, a pentafluoroethylgroup, a heptafluorobutyl group, a hexafluoroisopropyl group, aheptafluoroisopropyl group, a hexafluoro(2-methyl)isopropyl group, anonafluoro-butyl group, an octafluoroisobutyl group, a nonafluorohexylgroup, a nonafluoro-t-butyl group, a perfluoroisopentyl group, aperfluorooctyl group, a perfluoro(trimethyl)hexyl group, a2,2,3,3-tetrafluorocyclobutyl group, a perfluorocyclohexyl group and thelike. A hexafluoroisopropyl group, a heptafluoroisopropyl group, ahexafluoro(2-methyl)isopropyl group, an octafluoroisobutyl group, anonafluoro-t-butyl group, and a perfluoroisopentyl group are preferred,and a hexafluoroisopropyl group and a heptafluoroisopropyl group aremore preferred.

As the specific examples of the groups represented by formula (F4),—C(CF₃)₂OH, —C(C₂F₅)₂OH, —C(CF₃)(CH₃)OH, —CH(CF₃)OH, etc., areexemplified, and —C(CF₃)₂OH is preferred.

The specific examples of repeating units having a group represented byformula (F2), (F3) or (F4) are shown below. In the formulae, X₁represents a hydrogen atom, —CH₃, —F or CF₃; and X₂ represents —F or—CF₃.

As the partial structure having a silicon atom, resin (HP) is preferablya resin having an alkylsilyl structure (preferably a trialkylsilylgroup) or a cyclic siloxane structure.

As the specific examples of the alkylsilyl structure and the cyclicsiloxane structure, the groups represented by any of the followingformulae (CS-1) to (CS-3) are exemplified.

In formulae (CS-1) to (CS-3), R₁₂ to R₂₆ each represents a straightchain or branched alkyl group preferably having from 1 to 20 carbonatoms) or a cycloalkyl group (preferably having from 3 to 20 carbonatoms).

L₃ to L₅ each represents a single bond or a divalent linking group. Asthe examples of the divalent linking groups, a single group or acombination of two or more groups selected from the group consisting ofan alkylene group, a phenyl group, an ether group, a thioether group, acarbonyl group, an ester group, an amido group, a urethane group, and aurea group are exemplified.

The specific examples are shown below. In the formulae, X₁ represents ahydrogen atom, —CH₃, —F or —CF₃.

Further, resin (HP) may have a repeating unit represented by thefollowing formula (III):

In formula (III), R₄ represents an alkyl group, a cycloalkyl group, analkenyl group, or a cycloalkenyl group.

L₆ represents a single bond or a divalent linking group.

The alkyl group represented by R₄ in formula (III) is preferably astraight chain or branched alkyl group having from 3 to 20 carbon atoms.

The cycloalkyl group is preferably a cycloalkyl group having from 3 to20 carbon atoms.

The alkenyl group is preferably an alkenyl group having from 3 to 20carbon atoms.

The cycloalkenyl group is preferably a cycloalkenyl group having from 3to 20 carbon atoms.

The divalent linking group represented by L₆ is preferably an alkylenegroup (preferably having from 1 to 5 carbon atoms), or an oxy group.

When resin (HP) has a fluorine atom, the content of the fluorine atom ispreferably from 5 to 80 mass % to the molecular weight of resin (HP),more preferably from 10 to 80 mass %, and a repeating unit containing afluorine atom is preferably from 10 to 100 mass % in resin (HP), andmore preferably from 30 to 100 mass %.

The weight average molecular weight of the standard polystyreneequivalent of resin (HP) is preferably from 1,000 to 100,000, morepreferably from 1,000 to 50,000, and still more preferably from 2,000 to15,000.

Similarly to acid-decomposable resin (A), it is preferred that resin(HP) is as a matter of course little in impurities such as metals, andthe amount of the residual monomers and oligomer components ispreferably from 0 to 10 mass %, more preferably from 0 to 5 mass %, andstill more preferably from 0 to 1 mass %, by which a resist free fromforeign matters in the liquid and aging fluctuation of sensitivity canbe obtained. Further, in view of resolution, a resist form, thesidewalls of a resist pattern and roughness, the molecular weightdistribution (Mw/Mn, also referred to as the degree of dispersion) ofresin (HP) is preferably from 1 to 5, more preferably from 1 to 3, andstill more preferably from 1 to 2.

Various kinds of commercially available products can be used as resin(HP), or can be synthesized according to ordinary methods (e.g., radicalpolymerization). For instance, as ordinary methods, a batchpolymerization method of dissolving a monomer and an initiator in asolvent and heating the solution to perform polymerization, and adropping polymerization method of adding a solution of a monomer and aninitiator to a heated solvent over 1 to 10 hours by dropping areexemplified, and the dropping polymerization method is preferred. As thereaction solvents, ethers, e.g., tetrahydrofuran, 1,4-dioxane, anddiisopropyl ether, ketones, e.g., methyl ethyl ketone and methylisobutyl ketone, ester solvents, e.g., ethyl acetate, aide solvents,e.g., dimethylformamide and dimethyacetamide, and the later-describedsolvents capable of dissolving the composition of the invention, e.g.,propylene glycol monomethyl ether acetate, propylene glycol monomethylether, and cyclohexanone are exemplified. It is more preferred to usethe same solvent in polymerization as the solvent used in the resistcomposition of the invention, by which the generation of particlesduring preservation can be restrained.

It is preferred to perform polymerization reaction in the atmosphere ofinert gas such as nitrogen or argon. Polymerization is initiated withcommercially available radical polymerization initiators (e.g., azoinitiators, peroxide and the like). As radical polymerizationinitiators, azo initiators are preferred, and azo initiators having anester group, a cyano group, or a carboxyl group are preferred. Aspreferred initiators, azobisisobutyronitrile,azobis-dimethylvaleronitrile, dimethyl-2,2′-azobis(2-methyl-propionate),etc., are exemplified. The concentration of the reaction product is from5 to 50 mass %, and preferably from 30 to 50 mass %. The reactiontemperature is generally from 10 to 150° C., preferably from 30 to 120°C., and more preferably from 60 to 100° C.

After termination of the reaction, the reaction product is cooled toroom temperature, and purified. Ordinary methods can be applied topurification, e.g., a method of liquid-liquid extraction of removingresidual monomer and oligomer components by water washing and combiningappropriate solvents, a method of purification in a state of solution,such as ultrafiltration of removing only residual monomers having amolecular weight lower than a specific molecular weight by extraction, areprecipitation method of removing residual monomers by dropping a resinsolution to a bad solvent to thereby solidify the resin in the badsolvent, and a method of purification in a solid state by washingfiltered resin slurry with a bad solvent can be used. For example, thereaction solution is brought into contact with a hardly soluble orinsoluble solvent (bad solvent) of the resin in an amount of 10 times orless the volume of the reaction solution, preferably from 10 to 5 times,whereby the resin is precipitated as a solid.

The solvents for use in precipitation or reprecipitation from a polymersolution precipitation or reprecipitation solvents) should be sufficientso long as they are bad solvents of the polymer, and according to thekind of the polymer the solvent can be used by arbitrarily selectingfrom hydrocarbons, halogenated hydrocarbons, nitro compounds, ethers,ketones, esters, carbonates, alcohols, carboxylic acids, water, andmixed solvents containing these solvents. Of these solvents, solventscontaining at least alcohols (especially, methanol, etc.) or water arepreferred as the precipitation or reprecipitation solvents.

The use amount of a precipitation or reprecipitation solvent can bearbitrarily selected taking efficiency and yield into consideration, butgenerally the amount is from 100 to 10,000 mass parts per 100 mass partsof the polymer solution, preferably from 200 to 2,000 mass parts, andmore preferably from 300 to 1,000 mass parts.

The temperature in precipitation or reprecipitation can be arbitrarilyselected taking efficiency and workability into consideration, but thetemperature is generally from 0 to 50° C. or so, and preferably aroundroom temperature (e.g., from 20 to 35° C. or so). Precipitation orreprecipitation can be carried out according to known methods such as abatch system and a continuous system with generally used mixers, e.g., astirring tank.

A precipitated or reprecipitated polymer is generally subjected toordinary solid-liquid separation such as filtration and centrifugation,and then drying, and offered to use. Filtration is performed with afilter resisting to solvents preferably under pressure. Drying isgenerally carried out under atmospheric pressure or reduced pressure(preferably under reduced pressure), at a temperature of from 30 to 100°C. or so, and preferably from 30 to 50° C. or so.

Incidentally, a resin may be dissolved in a solvent after once beingprecipitated and separated, and then may be brought into contact with ahardly soluble or insoluble solvent of the resin. That is, a methodcomprising the following processes can be used: after termination of theradical polymerization reaction, the polymer is brought into contactwith a hardly soluble or insoluble solvent of the polymer to therebyprecipitate a resin (process a), the resin is separated from thesolution (process b), the resin is again dissolved in a solvent toprepare resin solution A (process c), a resin as a solid is precipitatedby bringing resin solution A into contact with a hardly soluble orinsoluble solvent of the resin in an amount of less than 10 times thevolume of resin solution A (preferably 3 times or less) process d), andthe precipitated resin is separated (process e).

The specific examples of resin (C) are shown below. Further, in thefollowing table, the molar ratio of repeating units (corresponding toeach repeating unit from the left hand in order) in each resin, weightaverage molecular weight, and the degree of dispersion are shown.

TABLE 1 Resin Composition Mw Mw/Mn HR-1 50/50 8,800 2.1 HR-2 50/50 5,3001.9 HR-3 50/50 6,200 1.9 HR-4 100 12,000 2.0 HR-5 50/50 5,800 1.9 HR-640/60 13,000 2.2 HR-7 60/40 9,800 2.2 HR-8 50/50 8,000 2.0 HR-9 50/5010,900 1.9 HR-10 50/50 6,900 1.9 HR-11 60/40 8,800 1.5 HR-12 68/3211,000 1.7 HR-13 100 8,000 1.4 HR-14 100 8,500 1.4 HR-i5 80/20 13,0002.1 HR-16 70/30 18,000 2.3 HR-17 50/50 5,200 1.9 HR-18 50/50 10,200 2.2HR-19 60/40 7,200 2.2 HR-20 32/32/36 5,600 2.0 HR-21 30/30/40 9,600 1.6HR-22 40/40/20 12,000 2.0 HR-23 100 6,800 1.6 HR-24 50/50 7,900 1.9HR-25 40/30/30 5,600 2.1 HR-26 50/50 6,800 1.7 HR-27 50/50 5,900 1.6HR-28 49/51 6,200 1.8 HR-29 50/50 8,000 1.9 HR-30 30/40/30 9,600 2.3HR-31 30/40/30 9,200 2.0 HR-32 40/29/31 3,200 2.1 HR-33 90/10 6,500 2.2HR-34 50/50 7,900 1.9 HR-35 20/30/50 10,800 1.6 HR-36 50/50 2,200 1.9HR-37 50/50 5,900 2.1 HR-38 40/20/30/10 14,000 2.2 HR-39 50/50 5,500 1.8HR-40 50/50 10,600 1.9 HR-41 50/50 8,600 2.3 HR-42 100 6,900 2.5 HR-4350/50 9,900 2.3

A film that is hardly soluble in an immersion liquid (hereinafter alsoreferred to as “topcoat”) may be provided between a positive resist filmcomprising the positive resist composition of the invention and animmersion liquid so as to prevent the resist film from being in contactwith the immersion liquid directly. The necessary functions required ofa topcoat are aptitude for coating on the upper layer of a resist, thetransparency to radiation, in particular, transparency to light of 193nm, and the insolubility in an immersion liquid. It is preferred that atopcoat is not mixed with a resist and capable of being coated uniformlyon a resist upper layer.

From the viewpoint of the transparency to 193 nm, polymers notcontaining aromatic groups in abundance are preferred as a topcoat.Specifically, hydrocarbon polymers, acrylic acid ester polymers,polymethacrylic acid, polyacrylic acid, polyvinyl ether,silicon-containing polymers and fluorine-containing polymers areexemplified. Hydrophobic resins (HP) are also preferably used as atopcoat. Considering that impurities eluting from a topcoat to animmersion liquid soil an optical lens, the residual monomer componentsof the polymer contained in a topcoat is preferably less.

When a topcoat is peeled, a developing solution may be used, or aremover may be used separately. As the remover, solvents low in osmosisinto a resist film are preferred. In view of capable of performingpeeling process at the same time with the development process of aresist film, peeling by an alkali developing solution is preferred. Fromthe viewpoint of peeling by an alkali developing solution, a topcoat ispreferably acidic, but from the point of non-intermixture with a resistfilm, a topcoat may be neutral or alkaline.

Resolution increases when there is no difference in the refractiveindexes between a topcoat and an immersion liquid. When water is used asthe immersion liquid in an ArF excimer laser (wavelength: 193 nm)exposure light source, it is preferred that the refractive index of thetopcoat for ArF immersion exposure is preferably near the refractiveindex of the immersion liquid. For bringing the refractive index of thetopcoat near to that of the immersion liquid, it is preferred for thetopcoat to contain a fluorine atom. Further, from the viewpoint of thetransparency and refractive index, the topcoat is preferably a thinfilm.

It is preferred that a topcoat should not be mixed with a resist film,and further not mixed with an immersion liquid. From this point of view,when water is used as the immersion liquid, the solvent for use in thetopcoat is preferably a medium that is hardly soluble in the solventused in the resist composition and non-water-soluble. Further, when theimmersion liquid is an organic solvent, the topcoat may be water-solubleor non-water-soluble.

(D) Solvent:

For using the resist composition of the invention, the above componentsare dissolved in a prescribed solvent. As the solvents, e.g., alkyleneglycol monoalkyl ether carboxylate, alkylene glycol monoalkyl ether,alkyl lactate, alkyl alkoxypropionate, cyclic lactone having from 4 to10 carbon atoms, a monoketone compound having from 4 to 10 carbon atomswhich may contain a ring, alkylene carbonate, alkyl alkoxy acetate, andalkyl pyruvate can be exemplified.

As the alkylene glycol monoalkyl ether carboxylate, e.g., propyleneglycol monomethyl ether acetate, propylene glycol monoethyl etheracetate, propylene glycol monopropyl ether acetate, propylene glycolmonobutyl ether acetate, propylene glycol monomethyl ether propionate,propylene glycol monoethyl ether propionate, ethylene glycol monomethylether acetate, ethylene glycol monoethyl ether acetate are preferablyexemplified.

As the alkylene glycol monoalkyl ether, e.g., propylene glycolmonomethyl ether, propylene glycol monoethyl ether, propylene glycolmonopropyl ether, propylene glycol monobutyl ether, ethylene glycolmonomethyl ether, and ethylene glycol monoethyl ether are preferablyexemplified.

As the alkyl lactate, e.g., methyl lactate, ethyl lactate, propyllactate, and butyl lactate are preferably exemplified.

As the alkyl alkoxypropionate, e.g., ethyl 3-ethoxy-propionate, methyl3-methoxypropionate, methyl 3-ethoxy-propionate, and ethyl3-methoxypropionate are preferably exemplified.

As the cyclic lactone having from 4 to 10 carbon atoms, e.g.,β-propiolactone, β-butyrolactone, γ-butyrolactone,α-methyl-γ-butyrolactone, β-methyl-γ-butyrolactone, γ-valerolactone,γ-caprolactone, γ-octanoic lactone, and α-hydroxy-γ-butyrolactone arepreferably exemplified.

As the monoketone compound having from 4 to 10 carbon atoms which maycontain a ring, e.g., 2-butanone, 3-methyl-butanone, pinacolone,2-pentanone, 3-pentanone, 3-methyl-2-pentanone, 4-methyl-2-pentanone,2-methyl-3-pentanone, 4,4-dimethyl-2-pentanone,2,4-dimethyl-3-pentanone, 2,2,4,4-tetramethyl-3-pentanone, 2-hexanone,3-hexanone, 5-methyl-3-hexanone, 2-heptanone, 3-heptanone, 4-heptanone,2-methyl-3-heptanone, 5-methyl-3-heptanone, 2,6-dimethyl-4-heptanone,2-octanone, 3-octanone, 2-nonane, 3-nonane, 5-nonane, 2-decanone,3-decanone, 4-decanone, 5-hexen-2-one, 3-penten-2-one, cyclopentanone,2-methylcyclopentanone, 3-methylcyclopentanone,2,2-ditmethylcyclopentanone, 2,4,4-trimethylcyclopentanone,cyclohexanone, 3-methylcyclo-hexanone, 4-methylcyclohexanone,4-ethylcyclohexanone, 2,2-dimethylcyclohexanone,2,6-dimethylcyclohexanone, 2,2,6-trimethylcyclohexanone, cycloheptanone,2-methyl-cycloheptanone, and 3-methylcycloheptanone are preferablyexemplified.

As the alkylene carbonate, e.g., propylene carbonate, vinylenecarbonate, ethylene carbonate, and butylene carbonate are preferablyexemplified.

As the alkyl alkoxy acetate, e.g., 2-methoxyethyl acetate, 2-ethoxyethylacetate, 2-(2-ethoxyethoxy)ethyl acetate, 3-methoxy-3-methylbutylacetate, and 1-methoxy-2-propyl acetate are preferably exemplified.

As the alkyl pyruvate, e.g., methyl pyruvate, ethyl pyruvate, and propylpyruvate are preferably exemplified.

Solvents having a boiling point of 130° C. or more under roomtemperature and atmospheric pressure are preferably used, andspecifically cyclopentanone, γ-butyrolactone, cyclohexanone, ethyllactate, ethylene glycol monoethyl ether acetate, propylene glycolmonomethyl ether acetate, ethyl 3-ethoxypropionate, ethyl pyruvate,2-ethoxyethyl acetate, 2-(2-ethoxyethoxy)ethyl acetate, and propylenecarbonate are exemplified.

In the invention, these solvents may be used alone or two or moresolvents may be used in combination.

In the invention, a mixed solvent comprising a solvent containing ahydroxyl group in the structure and a solvent not containing a hydroxylgroup in the structure may be used as an organic solvent.

As the solvent containing a hydroxyl group, ethylene glycol, ethyleneglycol monomethyl ether, ethylene glycol monoethyl ether, propyleneglycol, propylene glycol monomethyl ether, propylene glycol monoethylether, and ethyl lactate can be exemplified. Of these solvents,propylene glycol monomethyl ether and ethyl lactate are particularlypreferred.

As the solvent not containing a hydroxyl group, e.g., propylene glycolmonomethyl ether acetate, ethylethoxy propionate, 2-heptanone,γ-butyrolactone, cyclohexanone, butyl acetate, N-methylpyrrolidone,N,N-dimethylacetamide, and dimethyl sulfoxide can be exemplified. Ofthese solvents, propylene glycol monomethyl ether acetate, ethylethoxypropionate, 2-heptanone, γ-butyrolactone, cyclohexanone, and butylacetate are especially preferred, and propylene glycol monomethyl etheracetate, ethylethoxy propionate and 2-heptanone are most preferred.

In the invention, mixed solvents comprising two or more kinds includingpropylene glycol monomethyl ether acetate are preferred.

Further, mixed solvents comprising two or more kinds including ethyllactate and propylene glycol monomethyl ether acetate are morepreferred.

The mixing ratio (by mass) of the solvent containing a hydroxyl groupand the solvent not containing a hydroxyl group is from 1/99 to 99/1,preferably from 10/90 to 90/10, and more preferably from 20/80 to 60/40.A mixed solvent comprising 50 mass % or more of a solvent not containinga hydroxyl group is especially preferred in the point of coatinguniformity.

(E) Basic Compounds:

For reducing the fluctuation of performances due to aging from exposureto heating, it is preferred for the positive resist composition of theinvention to contain basic compound (E).

As preferred basic compounds, compounds having a structure representedbe any of the following formulae (A) to (E) can be exemplified.

In formulae (A) to (E), R²⁰⁰, R²⁰¹ and R²⁰², which may be the same ordifferent, each represents a hydrogen atom, an all group having from 1to 20 carbon atoms, a cycloalkyl group having from 3 to 20 carbon atoms,or an aryl group having from 6 to 20 carbon atoms, and R²⁰¹ and R²⁰² maybe bonded to each other to form a ring.

The alkyl group may be substituted or substituted, and as the alkylgroup having a substituent, an aminoalkyl group having from 1 to 20carbon atoms, a hydroxyalkyl group having from 1 to 20 carbon atoms, anda cyanoalkyl group having from 1 to 20 carbon atoms are preferred.

R²⁰³, R²⁰⁴, R²⁰⁵ and R²⁰⁶, which may be the same or different, eachrepresents an alkyl group having from 1 to 20 carbon atoms.

These alkyl groups in formulae (A) to (E) are more preferablyunsubstituted.

As the basic compounds, e.g., substituted or unsubstituted primary,secondary and tertiary aliphatic amines, aromatic amines, heterocyclicamines, amide derivatives, imide derivatives, and nitrogen-containingcompounds having a cyano group can be exemplified. Of these compounds)aliphatic amines, aromatic amines and heterocyclic amines are preferred.As the preferred substituents that the basic compounds may have, anamino group, an alkyl group, an alkoxyl group, an acyl group, an acyloxygroup, an aryl group, an aryloxy group, a nitro group, a cyano group, anester group and a lactone group are exemplified.

These basic compounds are used alone or two or more in combination.

In the resist composition of the invention, it is preferred that basiccompound (E) is a triethanolamine compound.

The use amount of the basic compounds is generally from 0.001 to 10 mass% based on the solids content of the positive resist composition, andpreferably from 0.01 to 5 mass %.

The proportion of use amount of the acid generator to the basic compoundin a composition is preferably acid generator/basic compound (molarratio) of from 2.5 to 300, That is, from the points of sensitivity andresolution, the molar ratio is preferably 2.5 or more, and in view ofthe restraint of the reduction of resolution by the thickening of aresist pattern due to aging from exposure to heating treatment, themolar ratio is preferably 300 or less. More preferably acidgenerator/basic compound (molar ratio) is from 5.0 to 200, and stillmore preferably from 7.0 to 150.

(F) Surfactant:

It is preferred for the positive resist composition in the invention tofurther contain surfactant, and it is more preferred to contain eitherone or two or more of fluorine and/or silicon surfactants (a fluorinesurfactant, a silicon surfactant, a surfactant containing both afluorine atom and a silicon atom).

By containing these surfactant, it becomes possible for the positiveresist composition in the invention to provide a resist patternexcellent in sensitivity and resolution, and low in defects in adhesionand development in using an exposure light source of 250 nm or lower, inparticular, 220 nm or lower.

These fluorine and/or silicon surfactants are disclosed, e.g., inJP-A-62-36663, JP-A-61-226746, JP-A-61-226745, JP-A-62-170950,JP-A-63-34540, JP-A-7-230165, JP-A-8-62834, JP-A-9-54432, JP-A-9-5988,JP-A-2002-277862, U.S. Pat. Nos. 5,405,720, 5,360,692, 5,529,881,5,296,330, 5,436,098, 5,576,143, 5,294,511 and 5,824,451. Thecommercially available surfactants shown below can also be used as theyare.

As the commercially available fluorine or silicon surfactants that canbe used in the invention, e.g., Eftop EF301 and EF303 (manufactured byShin-Akita Kasei Co., Ltd.), Fluorad FC 430, 431 and 4430 (manufacturedby Sumitomo 3M Limited), Megafac F171, F173, F176, F189, F113, F110,F177, F120, and R08 (manufactured by Dainippon Ink and Chemicals Inc.),Sarfron S-382, SC 101, 102, 103, 104, 105 and 106 (manufactured by ASAHIGLASS CO., LTD.), Troy Sol S-366 (manufactured by Troy Chemical Co.,Ltd.), GF-300 and Gf-150 (manufactured by TOAGOSET CO., LTD.), SarfronS-393 (manufactured by SEIMI CHEMICAL CO., LTD.), Eftop EF121, EF122A,EF122B, RF122C, EF125M, EF135M, EF351, 352, EF801, EF802, and EF601(manufactured by JEMCO INC.), PF636, PF6S6, PF6320 and PF6520(manufactured by OMNOVA), and FTX-204D, 208G, 218G, 230G, 204D, 208D,212D, 218, and 222D (manufactured by NEOS) are exemplified. In addition,polysiloxane polymer KP-341 (manufactured by Shin-Etsu Chemical Co.,Ltd.) can also be used as a silicon surfactant.

In addition to these known surfactants as exemplified above, surfactantsusing polymers having fluoro-aliphatic groups derived fromfluoro-aliphatic compounds manufactured by a telomerization method (alsocalled a telomer method) or an oligomerization method (also called anoligomer method) can be used, Fluoro-aliphatic compounds can besynthesized by the method disclosed in JP-A-2002-90991.

As the polymers having fluoro-aliphatic groups, copolymers of monomershaving fluoro-aliphatic groups and at least one of (poly(oxyalkylene))acrylate and (poly-(oxyalkylene)) methacrylate are preferred, and theymay be distributed at random or may be block copolymerized. As thepoly(oxyalkylene) groups, a poly(oxyethylene) group, apoly(oxypropylene) group, and a poly(oxybutylene) group are exemplified.The polymers may be units having alkylenes different in chain length inthe same chain length, such as a block combination of poly(oxyethyleneand oxypropylene and oxyethylene), and a block combination ofpoly(oxyethylene and oxypropylene). In addition, the copolymers ofmonomers having fluoro-aliphatic groups and poly(oxyalkylene)acrylate(or methacrylate) may be not only bipolymers but also terpolymers orhigher polymers obtained by copolymerization of monomers havingdifferent two or more kinds of fluoro-aliphatic groups or different twoor more kinds of poly(oxyalkylene)acrylates (or methacrylates) at thesame time.

For example, as commercially available surfactants, Megafac F178, F470,F473, F475, F476 and F472 (manufactured by Dainippon Ink and ChemicalsInc.) can be exemplified. Further, copolymers of acrylate (ormethacrylate) having a C₆F₁₃ group and poly(oxyalkylene)acrylate (ormethacrylate), and copolymers of acrylate (or methacrylate) having aC₃F₇ group, poly(oxyethylene)acrylate (or methacrylate), andpoly(oxy-propylene)acrylate (or methacrylate) can be exemplified.

In the invention, surfactants other than fluorine and/or siliconsurfactants can also be used. Specifically, nonionic surfactants, suchas polyoxyethylene alkyl ethers, e.g., polyoxyethylene lauryl ether,polyoxyethylene stearyl ether, polyoxyethylene cetyl ether,polyoxyethylene oleyl ether, etc., polyoxyethylene alkylallyl ether,e.g., polyoxyethylene octylphenol ether, polyoxyethylene nonylphenolether, etc., polyoxyethylene-polyoxypropylene block copolymers, sorbitanfatty acid esters, e.g., sorbitan monolaurate, sorbitan monopalmitate,sorbitan monostearate, sorbitan monooleate, sorbitan trioleate, sorbitantristearate, etc., and polyoxy-ethylene sorbitan fatty acid esters,e.g., polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitanmonopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylenesorbitan trioleate, polyoxyethylene sorbitan tristearate, etc., can beexemplified.

These surfactants may be used by one kind alone, or may be used incombination of some kinds.

The use amount of surfactants is preferably in the proportion of from0.0001 to 2 mass % based on all the amount of the positive resistcomposition (excluding solvents), and more preferably from 0.001 to 1mass %.

(G) Alkali-Soluble Resin:

The positive resist composition of the invention can further containresin (G) not containing an acid-decomposable group, insoluble in waterand soluble in an alkali developing solution, by which sensitivity isimproved.

Novolak resins having a molecular weight of from 1,000 to 20,000 or so,and polyhydroxystyrene derivatives having a molecular weight of from3,000 to 50,000 or so can be used as such alkali-soluble resins. Sincethese resins are great in absorption of rays of 250 nm or less, it ispreferred to use these resins by partially hydrogenating or in an amountof 30 mass % or less of the total resin amount.

Resins containing, as an alkali-soluble group, a carboxyl group can alsobe used. For the purpose of improving dry etching resistance, it ispreferred for the resins containing a carboxyl group to have amonocyclic or polycyclic alicyclic hydrocarbon group. Specifically,copolymers of methacrylic acid ester having an alicyclic hydrocarbonstructure not showing an acid-decomposing property and (meth)acrylicacid, and resins of (meth)acrylic acid ester of alicyclic hydrocarbongroup having carboxyl groups at terminals are exemplified.

(H) Carboxylic Acid Onium Salt:

The positive resist composition of the invention may contain carboxylicacid onium salt (H). As the carboxylic acid onium salt, carboxylic acidsulfonium salt, carboxylic acid iodonium salt, carboxylic acid ammoniumsalt, etc., can be exemplified. As carboxylic acid onium salt (H),iodonium salt and sulfonium salt are especially preferred. It ispreferred that the carboxylate residue of carboxylic acid onium salt (H)of the invention does not contain an aromatic group and a carbon-carbondouble bond. An especially preferred anion moiety is a straight chain orbranched, monocyclic or polycyclic alkylcarboxylate anion having from 1to 30 carbon atoms, and the carboxylate anion in which a part or all ofthe alkyl groups are substituted with fluorine atoms is more preferred.An oxygen atom may be contained in the alkyl chain, by which thetransparency to the lights of 220 nm or less is ensured, sensitivity andresolution are enhanced, and pitch dependency and exposure margin areimproved.

As fluorine-substituted carboxylate anions, anions such as fluoroaceticacid, difluoroacetic acid, trifluoroacetic acid, pentafluoropropionicacid, heptafluorobutyric acid, nonafluoropentanoic acid,perfluorododecanoic acid, perfluorotridecanoic acid,perfluorocyclohexanecarboxylic acid, 2,2-bistrifluoromethylpropionicacid, etc., are exemplified.

These carboxylic acid onium salts (H) can be synthesized by reactingsulfonium hydroxide, iodonium hydroxide, or ammonium hydroxide andcarboxylic acid with silver oxide in an appropriate solvent.

The content of carboxylic acid onium salt (H) in a composition isgenerally from 0.1 to 20 mass % to all the solids content of thecomposition, preferably from 0.5 to 10 mass %, and more preferably from1 to 7 mass %.

Other Additives:

The positive resist composition of the invention may further contain, ifnecessary, dyes, plasticizers, light-sensitizers, light absorbers, andcompounds for accelerating solubility in a developing solution (e.g.,phenolic compounds having a molecular weight of 1,000 or less, alicyclicor aliphatic compounds having a carboxyl group).

Such phenolic compounds having a molecular weight of 1,000 or less canbe easily synthesized with referring to the methods disclosed, e.g., inJP-A-4-122938, JP-A-2-28531, U.S. Pat. No. 4,916,210, and EP 219,294.

As the specific examples of the alicyclic or aliphatic compounds havinga carboxyl group, carboxylic acid derivatives having a steroidstructure, e.g., cholic acid, deoxycholic acid, and lithocholic acid,adamantanecarboxylic acid derivatives, adamantanedicarboxylic acid,cyclohexanecarboxylic acid, cyclohexanedicarboxylic acid, etc., areexemplified, but the invention is not limited to these compounds.

Physical Properties of the Resist Composition:

From the improvement of resolution, the positive resist composition ofthe invention is preferably used in a film thickness of from 30 to 250nm, and more preferably from 30 to 200 nm of film thickness. Such a filmthickness can be obtained by setting the concentration of solids contentin the positive resist composition in a proper range having appropriateviscosity to thereby improve a coating property and a film-formingproperty.

The concentration of all the solids content in the positive resistcomposition is generally from 1 to 10 mass %, more preferably from 1 to8 mass %, and still more preferably from 1.0 to 7.0 mass %.

Pattern-Forming Method:

The positive resist composition in the invention is used by dissolvingthe above components in a prescribed organic solvent, preferably in amixed solvent as described above, filtering the resulting solutionthrough a filter, and coating the solution on a prescribed support asfollows. Filters for filtration are preferably made ofpolytetrafluoroethylene, polyethylene or nylon having a pore diameter ofpreferably 0.1 μm or less, more preferably 0.05 μm or less, and stillmore preferably 0.03 μm or less.

For example, a positive resist composition is coated on a substrate suchas the one used in the manufacture of precision integrated circuitdevices (e.g., silicon/silicon dioxide coating) by an appropriatecoating method with a spinner or a coater and dried to form aphotosensitive film.

The photosensitive film is then irradiated with actinic ray or radiationthrough a prescribed mask, and the exposed film is preferably subjectedto baking (heating), and then development and rinsing, whereby a goodpattern can be obtained.

As actinic rays or radiation, infrared rays, visible rays, ultravioletrays, far ultraviolet rays, X-rays and electron beams can beexemplified, preferably far ultraviolet rays of wavelengths of 250 nm orless, and more preferably 220 nm or less. Specifically, a KrF excimerlaser (248 nm), an ArF excimer laser (193 nm), an F2 excimer laser (157nm), X-rays and electron beams are exemplified, and preferably rayshaving wavelengths of from 1 to 200 nm, in particular, an ArF excimerlaser, an F₂ excimer laser, EUV (13 nm), and electron beams arepreferably used.

In a development process, an alkali developing solution is used asfollows. As the alkali developing solution of a resist composition,alkali aqueous solutions of inorganic alkalis, e.g., sodium hydroxide,potassium hydroxide, sodium carbonate, sodium silicate, sodiummetasilicate, aqueous ammonia, etc., primary amines, e.g., ethylamine,n-propylamine, etc., secondary amines, e.g., diethylamine,di-n-butylamine, etc., tertiary amines, e.g., triethylamine,methyldiethylamine, etc., alcohol amines, e.g., dimethylethanolamine,triethanolamine, etc., quaternary ammonium salts, e.g.,tetramethylammonium hydroxide, tetraethylammonium hydroxide, etc., andcyclic amines, e.g., pyrrole, piperidine, etc., can be used.

An appropriate amount of alcohols and surfactants may be added to thesealkali developing solutions.

The alkali concentration of the alkali developing solutions is generallyfrom 0.1 to 20 mass %.

The pH of the alkali developing solutions is generally from 10.0 to15.0.

Further, an appropriate amount of alcohols and surfactants may be addedto the alkali aqueous solution.

Pure water can also be used as a rinsing liquid and an appropriateamount of surfactant may be added to the rinsing liquid.

After development process or rinsing process, a process to remove thedeveloping solution or rinsing liquid on the pattern can be performedwith a supercritical fluid.

At the time of irradiation with actinic ray or radiation, exposure(immersion exposure) may be performed by filling a liquid (an immersionmedium) having higher refractive index than that of air between a resistfilm and a lens, by which resolution can be raised. As the immersionmedium, any liquids can be used so long as they are liquids higher inrefractive index than air, but pure water is preferred. An overcoatlayer may further be provided on a photosensitive film so that animmersion medium is not directly in contact with the photosensitive filmin performing immersion exposure, by which the elution of thecomposition from the photosensitive film to the immersion medium isrestrained and development defect can be reduced.

An immersion liquid for use in immersion exposure is described below.

An immersion liquid having a temperature coefficient of refractive indexas small as possible is preferred so as to be transparent to theexposure wavelength and to hold the distortion of optical imagereflected on the resist to the minimum. In particular, when the exposurelight source is an ArF excimer laser (wavelength: 193 nm), it ispreferred to use water as the immersion liquid for easiness ofavailability and easy handling property, in addition to the abovepoints.

Further, in view of the improvement of refractive index, a medium havinga refractive index of 1.5 or more can also be used, e.g., an aqueoussolution and an organic solvent can be used as the medium.

When water is used as an immersion liquid, to reduce the surface tensionof water and to increase the surface activity, a trace amount ofadditive (a liquid) that does not dissolve the resist layer on a waferand has a negligible influence on the optical coating of the lowersurface of a lens may be added. As the additive, aliphatic alcoholshaving a refractive index almost equal to the refractive index of waterare preferred, specifically methyl alcohol, ethyl alcohol and isopropylalcohol are exemplified. By the addition of an alcohol having arefractive index almost equal to that of water, even if the alcoholcomponent in water is evaporated and the concentration of the content ischanged, the fluctuation of the refractive index of the liquid as awhole can be made extremely small. On the other hand, when substancesopaque to the light of 193 nm or impurities largely different from waterin a refractive index are mixed, these substances bring about thedistortion of the optical image reflected on the resist. Accordingly,the water used is preferably distilled water. Further, pure waterfiltered through an ion exchange filter may be used.

The electric resistance of water is preferably 18.3 MΩ·cm or higher, andTOC (organic substance concentration) is preferably 20 ppb or lower.Further, it is preferred that water has been subjected to deaerationtreatment.

It is possible to heighten lithographic performance by increasing therefractive index of an immersion liquid. From such a point of view,additives capable of heightening a refractive index may be added towater, or heavy water (D₂O) may be used in place of water.

EXAMPLE 1

The invention will be described in detail with reference to examples,but the invention should not be construed as being restricted thereto.

SYNTHESIS EXAMPLE Synthesis of Resin (C)

Heptafluorobutyl methacrylate and t-butyl methacrylate in the proportionof 50/50 (molar ratio) are put in a reaction vessel and dissolved incyclohexanone to prepare 450 g of a solution having the concentration ofsolids content of 22%. To the solution is added 5 mol % of apolymerization initiator V-601 (manufactured by Wako Pure ChemicalIndustries Ltd.), and, in the nitrogen atmosphere, the solution isdropped to 50 ml of cyclohexanone heated at 80° C. over 2 hours. Aftercompletion of dropping, the reaction solution is stirred for 2 hours toobtain reaction solution (HR-1). After termination of the reaction,reaction solution (HR-1) is cooled to room temperature, crystallizedwith ten times the amount of methanol, the precipitated white powder isfiltered and the objective resin (HR-1) is recovered.

The polymer composition ratio found from ¹H NMR is 50/50 (molar ratio).The weight average molecular weight as the standard polystyreneequivalent found by the GPC measurement is 8,800, and the degree ofdispersion is 2.1.

Each of other resins (C) is manufactured in the same manner.

Synthesis of Resin (A)

2-Ethyl-2-adamantyl methacrylate (0.4 mol), 0.4 mol ofα-(γ-butyrolactone) methacrylate, and 0.2 mol of 3-hydroxy-1-adamantylmethacrylate are dissolved in 600 ml of cyclopentanone, and 0.1 mol ofAIBN is added thereto and dissolved. The obtained solution is heated at65 to 70° C. for 3 hours. The obtained reaction solution is poured into3 liters of well-stirred isopropanol, and the precipitated solid isseparated by filtration. The obtained solid is dissolved in 600 ml ofTHF, poured into 3 liters of well-stirred methanol, the precipitatedsolid is separated by filtration and dried to obtain the following shownresin 1.

Resins 2 to 6 are synthesized in the same manner. The structures,composition ratios, weight average molecular weights (Mw), and thedegrees of dispersion (Mw/Mn) of the resins are shown below.

1

Mw =10700Mw/Mn =1.81 2

Mw =9800Mw/Mn =1.73 3

Mw =8600Mw/Mn =1.82 4

Mw =7800Mw/Mn =1.79 5

Mw =8900Mw/Mn =1.71 6

Mw =9200Mw/Mn =1.89 7

Mw =9100Mw/Mn =1.91 8

Mw =8900Mw/Mn =1.72 9

Mw =7100Mw/Mn =1.88 10

Mw =8600Mw/Mn =1.81

Preparation of Resist:

The components of each sample are dissolved in the solvent each shown inTable 2 below to prepare a solution having the concentration of solidscontent of 7 mass %, and the solution is filtered through a polyethylenefilter having a pore diameter of 0.1 μm to prepare a positive resistsolution. The prepared positive resist solution is evaluated by thefollowing methods. The results obtained are shown in Table 2. Inconnection with each component in Table 2, when two or more componentsare used, the ratio is shown in mass ratio.

Evaluation of Exposure: Water Mark

An organic antireflection film ARC29A (manufactured by Nissan ChemicalIndustries, Ltd.) is coated on a silicon wafer, and baked at 205° C. for60 seconds to form an antireflection film having a thickness of 78 nm.The prepared positive resist composition is coated thereon, and baked at110° C. for 60 seconds to form a resist film having a thickness of 150nm. The obtained wafer is subjected to pattern exposure with an ArFexcimer laser immersion scanner (NA: 0.85, scanning speed: 500 mm/s). Asthe immersion liquid, super pure water is used. Subsequently, the waferis baked at 110° C. for 60 seconds, and then subjected to developmentwith a tetramethylammonium hydroxide aqueous solution (2.38 mass %) for30 seconds, rinsing with pure water, and spin drying to obtain a resistpattern. After that, the distribution of defects is detected with KLA2360 (manufactured by KLA Tencor Corporation), and the shape of defectis observed with SEMVision (manufactured by AMAT).

A circular defect having a diameter of from 1 to 5 μm or so as shown inFIGURE is taken as water mark defect, and the number of the defects onthe wafer in a length of 300 mm is counted.

Evaluation of Exposure: Film Decrease Margin

An organic antireflection film ARC29A (manufactured by Nissan ChemicalIndustries, Ltd.) is coated on a silicon wafer, and baked at 205° C. for60 seconds to form an antireflection film having a thickness of 78 nm.The prepared positive resist composition is coated thereon, and baked at110° C. for 60 seconds to form a resist film having a thickness of 150nm. The obtained wafer is subjected to pattern exposure with an ArFexcimer laser immersion scanner (NA: 0.85). As the immersion liquid,super pure water is used. Subsequently the wafer is baked at 110° C. for60 seconds, and then subjected to development with a tetramethylammoniumhydroxide aqueous solution (2.38 mass %) for 30 seconds, rinsing withpure water, and spin drying to obtain a resist pattern. At this time,exposure quantity resolving 75 nm L/S (line and space) pattern in 1/1(Eo) and exposure quantity by which the film begins to be dissolved andthe rectangular shape of the pattern head is impaired by over exposure(ELoss) are found, and film decrease margin (over exposure margin) iscomputed according to the following expression.

Film decrease margin (%)=(ELoss−Eo)/Eo×100

TABLE 2 Water (A) (B) (C) (D) Basic Mark Film Example Resin AcidGenerator Resin Solvent Compound Surfactant Defect Decrease No. (2 g)(mg) (mg) (mass ratio) (mg) (mg) (number) Margin Example 1 1 z2 (80)HR-1 (4) SL-1/SL-2 (60/40) N-7 (7) W-1 (3) 5 5 Example 2 2 z51 (100)HR-5 (6) SL-2/SL-3 (60/40) N-1 (6) W-1 (3) 1 6 Example 3 3 z2/z62(20/100) HR-6 (10) SL-2/SL-3 (50/50) N-2 (4) W-1 (4) 6 4 Example 4 4z55/z65 (20/100) HR-7 (14) SL-2/SL-4 (60/40) N-3 (8) W-2 (4) 4 5 Example5 5 z55/z51 (20/80) HR-9 (8) SL-2/SL-4 (50/50) N-4 (6) W-3 (4) 4 6Example 6 6 z44/z65 (25/80) HR-10 (9) SL-2/SL-4/SL-5 (50/45/5) N-5 (9)W-4 (4) 2 6 Example 7 7 z55/z47 (30/80) HR-12 (18) SL-2/SL-3 (50/50) N-6(5) — 4 4 Example 8 8 z55 (100) HR-18 (14) SL-2/SL-4/SL-6 (50/45/5) N-7(6) W-5 (4) 6 4 Example 9 9 z44/z65 (50/50) HR-23 (3) SL-2/SL-3 (70/30)N-7 (9) W-6 (4) 5 5 Example 10 10 z59 (100) HR-26 (5) SL-2/SL-4 (60/40)N-7 (10) W-1 (4) 2 6 Example 11 1 z55/z65 (40/60) HR-34 (8) SL-2/SL-4(70/30) N-7 (7) W-6 (4) 4 5 Example 12 2 z55/z64 (20/80) HR-35 (6)SL-2/SL-3 (80/20) N-7 (6) W-6 (5) 6 4 Example 13 3 z47 (110) HR-41 (9)SL-2/SL-3 (50/50) N-7 (5) W-6 (6) 5 5 Example 14 4 z62 (120) HR-42 (10)SL-2/SL-4 (80/20) N-7 (5) W-6 (7) 1 6 Example 15 5 z55/z51 (40/60) HR-11(14) SL-2/SL-3/SL-4 (60/20/20) N-7 (6) W-6 (8) 1 5 Example 16 6 z65/z29(100/10) HR-13 (14) SL-2/SL-4 (80/20) N-6 (7) W-6 (9) 0 6 Example 17 7z66 (100) HR-14 (8) SL-2/SL-3/SL-4 (60/20/20) N-4 (8) W-1 (2) 2 4Example 18 8 z16 (90) HR-20 (9) SL-2/SL-4 (80/20) N-7 (9) W-1 (4) 4 5Example 19 9 z55 (80) HR-25 (11) SL-2/SL-3 (50/50) N-3 (10) W-1 (4) 6 6Example 20 10 z55/z57 (60/40) HR-27 (9) SL-2/SL-3 (50/50) N-7 (8) W-1(4) 5 5 Comparative 1 z2 (80) — SL-1/SL-2 (60/40) N-7 (7) W-1 (3) >100 2Example 1 Comparative 2 z51 (100) — SL-2/SL-3 (60/40) N-1 (6) W-1(3) >100 2 Example 2 Comparative 6 Z65/z29 (100/10) — SL-2/SL-4 (80/20)N-6 (7) W-6 (9) >100 2 Example 3 The signs in Table 2 are as follows.Acid generators are corresponding to those shown above. N-1:N,N-Dibutylaniline N-2: N,N-Dihexylaniline N-3: 2,6-DiisopropylanilineN-4: Tri-n-octylamine N-5: N,N-Dihydroxyethylaniline N-6:2,4-5-Triphenylimidazole N-7: Triethanolamine W-1: Megafac P176(fluorine surfactant, manufactured by Dainippon Ink and Chemicals Inc.)W-2: Megafac R08 (fluorine/silicon surfactant, manufactured by DainipponInk and Chemicals Inc.) W-3: Polysiloxane polymer KP-341 (siliconsurfactant, manufactured by Shin-Etsu Chemical Co., Ltd.) W-4: Troy SolS-366 (manufactured by Troy Chemical Co., Ltd.) W-5: PF656 (fluorinesurfactant, manufactured by OMNOVA) W-6: PF6320 (fluorine surfactant,manufactured by OMNOVA) SL-1: Cyclohexanone SL-2: Propylene glycolmonomethyl ether acetate SL-3: Ethyl lactate SL-4: Propylene glycolmonomethyl ether SL-5: γ-Butyrolactone SL-6: Propylene carbonate

According to the invention, a positive resist composition capable ofrestraining the occurrence of water marks at the time of immersionexposure and a pattern-forming method using the same can be provided.Further, the positive resist composition of the invention can reduce thedecrease of film thickness at the time of immersion exposure.

The entire disclosure of each and every foreign patent application fromwhich the benefit of foreign priority has been claimed in the presentapplication is incorporated herein by reference, as if fully set forth.

1. A positive resist composition comprising: (A) a resin capable ofincreasing the solubility in an alkali developing solution by the actionof an acid, comprising: (a1) a repeating unit selected from repeatingunits represented by following formulae (a1-1) to (a1-3); (a2) arepeating unit represented by a following formula (a2); and (a3) arepeating unit selected from repeating units represented by followingformulae (a3-1) to (a3-4); (B) a compound capable of generating an acidupon irradiation with actinic ray or radiation, (C) a resin comprising:at least one of a fluorine atom and a silicon atom; and a group selectedfrom following groups (x) to (z): (x) an alkali-soluble group, (y) agroup capable of decomposing by the action of an alkali developingsolution to increase the solubility in the alkali developing solution,and (z) a group capable of decomposing by the action of an acid; and (D)a solvent:

wherein R represents a hydrogen atom, a halogen atom, or an alkyl group;R′ represents an acid-decomposable group; each of R₁₂ and R₁₃independently represents a hydrogen atom, a methyl group, an ethylgroup, or a propyl group; R₁₄ represents an alicyclic group; and nrepresents an integer of from 0 to
 5. 2. The positive resist compositionaccording to claim 1, wherein the resin (A) further comprises: (a4) arepeating unit selected from repeating units represented followingformulae (a4-1) to (a4-3):

wherein R represents a hydrogen atom, a halogen atom, or an alkyl group.3. The positive resist composition according to claim 1, wherein theresin (C) comprises a repeating unit containing a lactone group.
 4. Thepositive resist composition according to claim 1, wherein the resin (C)is an alkali-soluble resin containing an alkyl group having a fluorineatom and from 1 to 4 carbon atoms, a cycloalkyl group having a fluorineatom, or an aryl group having a fluorine atom.
 5. The positive resistcomposition according to claim 1, wherein the resin (C) contains analcoholic hydroxyl group, and an alcohol moiety of the alcoholichydroxyl group is a fluorinated alcohol.
 6. The positive resistcomposition according to claim 1, wherein the solvent (D) is a mixedsolvent of two or more kinds of solvents comprising propylene glycolmonomethyl ether acetate.
 7. The positive resist composition accordingto claim 1, wherein the solvent (D) is a mixed solvent of two or morekinds of solvents comprising ethyl lactate and propylene glycolmonomethyl ether acetate.
 8. The positive resist composition accordingto claim 1, further comprising: (E) a basic compound.
 9. The positiveresist composition according to claim 1, wherein the compound (B) has atriphenyl sulfonium cation structure.
 10. The positive resistcomposition according to claim 1, wherein the basic compound (E) is atriethanolamine compound.
 11. The positive resist composition accordingto claim 1, wherein the compound (B) is a compound represented byfollowing formula (b-1) or (b-2);

wherein each of Rb₁, Rb₂ and Rb₃ represents an alkyl group, a cycloalkylgroup, or an aryl group, provided that at least one of Rb₁ to Rb₃represents an aryl group; Xb represents an alkylene fluoride grouphaving from 2 to 6 carbon atoms; and each of Yb and Zb independentlyrepresents an alkyl group.
 12. The positive resist composition accordingto claim 1, further comprising: at least one surfactant selected from asurfactant containing a fluorine atom, a surfactant containing a siliconatom, and a surfactant containing both a fluorine atom and a siliconatom.
 13. The positive resist composition according to claim 1, whereinthe resin (C) is a solid at 25° C.
 14. The positive resist compositionaccording to claim 1, wherein the resin (C) has a glass transitiontemperature of from 50 to 200° C.
 15. The positive resist compositionaccording to claim 1, wherein the resin (C) has a weight averagemolecular weight of from 1,000 to 50,000.
 16. The positive resistcomposition according to claim 1, wherein the resin (C) is contained ina proportion of from 0.1 to 5 mass % based on all solids content in thepositive resist composition.
 17. A pattern-forming method comprising:forming a resist film with the resist composition according to claim 1;exposing the formed resist film; and developing the exposed film.